Percentage and profit loss new version 4

METHODS
Eight Techniques
1
APPLICATIONS
In Commerce,
Geometry etc.,
2
LINKS
Profit & Loss &
other links
3
PERCENTAGE
SIX PHRASE – VEERARAGAVAN C.S
http://182.72.85.213:8080/AssessmentTool http://www.facebook.com/SixPhrase
https://twitter.com/sixphrase
PRESENTER NAME SIX PHRASE – The Finishing School 1 I

SESSION CONTENT
• In this session, we shall learn application of
percentage concept in problems in the areas
of geometry & commerce including profit /
loss.
• Percentage concepts used in other areas such
as alligations / mixtures are dealt under the
respective session topics.
02-03-2015
VEERARAGAVAN C S, APTITUDE TRAINER,
veeraa1729@gmail.com
2

X% of a Number
An x % increase
An x% decrease
40% OF 20 MEANS
40
100
𝑋20 = 8.
1) If 20% of a = b, then b% of 20 is the same as:
A.4% of a B. 5% of a C.20% of a D. None of these
20% of a = b 
20
100
𝑋𝑎 = 𝑏
b% of 20 =
𝑏
100
𝑋20
b% of 20 =
20
100
𝑋𝑎𝑋
1
100
𝑋20 =
4𝑎
100

X% of a Number
An x % increase
An x% decrease
Increase by 40% means 140% of that number.
III.The price of a product becomes `54 after it increases by 35%.
What was the original price of that product? 1)30 2)36 3)40 4)45
Increase by 35% means 135% of the price is 54.
135
100
𝑋 𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑝𝑟𝑖𝑐𝑒 = 54 Hence the original price is 54 𝑋
100
135
= 40.

X% of a Number
An x % increase
An x% decrease
Decrease by 40% means (100–40)60% of that number.
V. The price of a product is reduced to Rs.72 after it is decreased by
10%. What is the original price of the product? 1)84 2)90 3)96 4)80
Decreased by 10% means 90% of that price.
Hence the original price is 72 𝑋
100
90
= 80.
90
100
𝑋𝑜𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑝𝑟𝑖𝑐𝑒 = 72

Calculating a percent change
Basically, a percent is a simple
𝑝𝑎𝑟𝑡
𝑤ℎ𝑜𝑙𝑒
ratio
times 100. When they ask you to
calculate percent changes, and here you
have to be very careful with order, i.e.,
what’s the starting number and what’s
the ending number.
IMPORTANT: in a percent change, the
starting number is always 100%. Thus,
we can say:
Percent change =
𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑐ℎ𝑎𝑛𝑔𝑒
𝑆𝑡𝑎𝑟𝑡𝑖𝑛𝑔 𝑁𝑢𝑚𝑏𝑒𝑟
𝑋100
Here are a couple examples
a) Price increases from `400 to `500; find
the percentage increase.
Of course, that’s a change of `100, so
`100 divided by starting value of `400 is
0.25, times 100 is 25%. A move from `
400 to ` 500 is a 25% increase.
• b) Price decreases from ` 500 to ` 400;
find the percentage decrease.
• Change is still ` 100, but now the
starting value is ` 500, and `
100
500
=
0.20, times 100 is 20%. A move from
` 500 to ` 400 is a 20% decrease.
• BIG IDEA: Order matters. When you
change from one value to another
and want the percentage change, it
matters which value was the starting
value.
02-03-2015
6

PERCENT CHANGE
The population of a town increased from 1,75,000 to 2,62,500 in
a decade. The average percent increase of population per year
is: A.4.37% B.5% C.6% D.8.75%
Increase in 10 years = (262500 - 175000) = 87500.
Here the starting number is 175000.
Increase% =
87500
175000
𝑋100% = 50%.
Required average =
50
10
%= 5%.
02-03-2015
7

Percentage
increased by x % then
decreased by y % then
resulting effect in percent
+x – y –
𝑥𝑦
100
Increased by x% then again
increased by y% then
+x+y+
𝑥𝑦
100
Decreased by x% then
increased by y%
–x+y –
𝑥𝑦
100
Decreased by x% then again
decreased by y%
– x – y +
𝑥𝑦
100
02-03-2015
8
If the value of something is
I.If the price of a shirt is increased by 10%
than decreased by 10%. What is the
percent change?
+ 10 - 10 –
10 10
100
= - 1%
The best way to speed up calculations is to
eliminate the need of calculations.

9.Rajeev buys good worth Rs. 6650. He gets a
rebate of 6% on it. After getting the rebate, he
pays sales tax @ 10%. Find the amount he will
have to pay for the goods.
A. Rs. 6876.10 B. Rs. 6999.20
C. Rs. 6654 D. Rs. 7000
Total percentage = −6 + 10 −
60
100
= +3.4%
Amount he will pay = 6650 ∗
103.4
100
= 6876.10
02-03-2015
9

PERCENTAGE OF PROFIT & LOSS
100 oranges are bought at the rate of Rs. 350 and
sold at the rate of Rs. 48 per dozen.
The percentage of profit or loss is:
A. 14
2
7
% gain B.15% gain C. 14
2
7
% loss D.15 % loss
C.P of 100 oranges = Rs.350
S.P of 100 oranges =
48
12
x100 = 400.
Profit % =
400 −350
350
𝑥100 = 14
2
7
% gain
02-03-2015
10

Profit percentage
If the cost price of x articles is
equal to the selling price of y
articles, then the profit percentage
is given by: 𝑥 − 𝑦
100
𝑦
If Sudha sells 18 articles at the cost
price of 24 articles. Find her profit
percentage?
Here, x= 24 and y= 18
24 − 18
100
18
=
100
3
= 33
1
3
%
02-03-2015 11
Usual Method
Let C.P of 1 article be Rs.x
Then C.P of 24 articles =
24x
S.P of 18 articles = 24x
S.P of 1 article =
24𝑥
18
Profit % =
24𝑥
18
−𝑥
𝑥
𝑋100
= 24𝑥 − 18𝑥
100
18
=
100
3
= 33
1
3
%

QUANTITY
The cost price of 20 articles is the same as the
selling price of x articles.
If the profit is 25%, then the value of x is:
A. 15 B. 16 C. 18 D. 25
Profit% =
x−20
20
𝑥100= 25.
X – 20 = 5
X = 25.
02-03-2015
12

TOTAL GAIN / LOSS
A shopkeeper sells one transistor for Rs. 840 at a gain of 20%
and another for Rs. 960 at a loss of 4%.
His total gain or loss percent is:
A. 5
15
17
% loss B. 5
15
17
% gain C. 6
2
3
% gain D. None of these
C.P. of 1st transistor =
100
120
𝑥840 = Rs.700
C.P. of 2nd transistor =
100
96
x 960 = Rs.1000
So, total C.P. = Rs. (700 + 1000) = Rs. 1700.
Total S.P. = Rs. (840 + 960) = Rs. 1800.
Gain % =
1800 −1700
1700
x 100 = 5
15
17
% gain.
02-03-2015
13

PROFIT IN MIXTURE
A trader mixes 26 kg of rice at Rs. 20 per kg with 30 kg
of rice of other variety at Rs. 36 per kg and sells the
mixture at Rs. 30 per kg.
His profit percent is:
A. No profit, no loss B. 5%
C. 8% D. 10% E. None of these
C.P. of 56 kg rice = Rs. (26 x 20 + 30 x 36)
= Rs. (520 + 1080) = Rs. 1600.
S.P. of 56 kg rice = Rs. (56 x 30) = Rs. 1680.
Gain =
1680−1600
1600
𝑥100 = 5%
02-03-2015
14

SELLING PRICE
A man buys a cycle for Rs. 1400 and sells it at a loss of 15%.
What is the selling price of the cycle?
A. Rs. 1090 B. Rs. 1160
C. Rs. 1190 D. Rs. 1202
S.P =
85
100
𝑋1400= Rs.1190
02-03-2015
15

SELLING PRICE
The percentage profit earned by selling an article for Rs. 1920 is
equal to the percentage loss incurred by selling the same article
for Rs. 1280.
At what price should the article be sold to make 25% profit?
A. Rs. 2000 B. Rs. 2200
C. Rs. 2400 D. Data inadequate
SP1 – CP = CP – SP2 means CP =
SP1+SP2
2
=
1920+1280
2
=1600.
New SP =
125
100
x 1600 = Rs.2000.
02-03-2015
16

Selling Price
By selling a horse for Rs
570 a trader loses 5%. At
what price must he sell it to
gain 5%.
Selling Price(SP)
= given(Rs) X
100±𝑄
100±𝑔𝑖𝑣𝑒𝑛%
Selling Price
= 570 X
100+5
100−5
=Rs.630
02-03-2015
17
USUAL METHOD
S.P = 570 and loss 5%
C.P =
100
100−𝑙𝑜𝑠𝑠
𝑥𝑆. 𝑃
=
100
95
𝑥570
Profit = 5%
So new S.P
=
100+𝑃𝑅𝑂𝐹𝐼𝑇
100
𝑋𝐶. 𝑃
=
105
100
𝑥
100
95
𝑋570
=Rs.630

SELLING PRICE
When a plot is sold for Rs. 18,700, the
owner loses 15%.
At what price must that plot be sold in
order to gain 15%?
A. Rs. 21,000 B.Rs. 22,500
C. Rs. 25,300 D.Rs. 25,800
S.P = Given Amt x
100 ± 𝑄𝑢𝑒𝑠𝑡𝑖𝑜𝑛
100 ±𝑔𝑖𝑣𝑒𝑛 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒
= 18700 x
115
85
= Rs.25,300
02-03-2015
18
Given S.P = 18,700
Loss = 15%
C.P =
100
100 −loss
x S.P
=
100
85
X18700
Required = Profit 15%
S.P=
100+𝑝𝑟𝑜𝑓𝑖𝑡
100
𝑋𝐶. 𝑃
=
115
100
𝑋
100
85
𝑋18700

SELLING PRICE
A vendor bought toffees at 6 for a rupee. How
many for a rupee must he sell to gain 20%?
A. 3 B. 4 C. 5 D. 6
C.P of 6 toffees = `.1
S.P of 6 toffees =
120
100
𝑋1 =
120
100
For `
120
100
, no of toffees sold = 6.
For `1, no of toffees sold =
100
120
x 6 = 5.
02-03-2015
19

COST PRICE
On selling 17 balls at Rs. 720, there is a loss equal to
the cost price of 5 balls.
The cost price of a ball is:
A. Rs. 45B. Rs. 50
C. Rs. 55D. Rs. 60
(C.P. of 17 balls) - (S.P. of 17 balls) = (C.P. of 5 balls)
C.P. of 12 balls = S.P. of 17 balls = Rs.720.
C.P of 1 ball =
720
12
= Rs.60
02-03-2015
20

PERCENTAGE ERROR
2.A student multiplied a number by
3
5
instead of
5
3
. What is the
percentage error in the calculation?
A.34% B.44% C.54% D.64%
Error = correct value – wrong value =
5
3
−
3
5
=
16
15
Percentage error =
𝐸𝑟𝑟𝑜𝑟
𝐶𝑜𝑟𝑟𝑒𝑐𝑡
𝑋100 =
16
15
5
3
𝑋100=
16
15
𝑋
3
5
𝑋100
64%
02-03-2015
21

PERCENTAGE IN SETS
3.In a certain school, 20% of students are below 8 years
of age. The number of students above 8 years of age is
of the number of students of 8 years of age which is 48.
What is the total number of students in the school?
A.72 B.80 C.120 D.150 E.100
Number of students of 8 years of age = 48.
Number of students of 8 years above = 48.
80% of students = 96.
Hence No. of students = 96 𝑋
100
80
=120.
02-03-2015
22

PERCENTAGE IN SETS
5.In an election between two candidates, one got 55% of the
total valid votes, 20% of the votes were invalid. If the total
number of votes was 7500, the number of valid votes that the
other candidate got, was: A.2700 B.2900 C.3000 D.3100
Number of valid votes = 80% of 7500 = 6000.
Valid votes polled by other candidate = 45% of 6000=2700.
02-03-2015
23

PERCENTAGE IN SETS
6.Three candidates contested an election and received
1136, 7636 and 11628 votes respectively.
What percentage of the total votes did the winning
candidate get?
A. 57% B. 60% C. 65% D. 90%
Total number of votes polled = (1136 + 7636 + 11628) =
20400.
Required perecentage =
11628
20400
𝑋100% = 57%
02-03-2015
24

PERCENTAGE IN RATIO
4. Two numbers A and B are such that the sum of 5% of A and 4%
of B is two-third of the sum of 6% of A and 8% of B. Find the ratio
of A : B. A.2 : 3 B. 1 : 1 C. 3 : 4 D. 4 : 3
02-03-2015
25
5% of A + 4% of B =
2
(6% of A + 8% of B)
3
5
A +
4
B =
2
(
6
A +
8
B)
100 100 3 100 100
1
A +
1
B =
1
A +
4
B
20 25 25 75
1
-
1
A =
4
-
1
B
20 25 75 25
1
A =
1
B
100 75
5% of A + 4% of B =
2
3
6% 𝑜𝑓 𝐴 +
5% of A + 4% of B = 4% of A +
16
3
% of B
1% of A =
16
3
− 4 % of B
1% of A =
4
3
% of B
A
=
100
=
4
.
B 75 3 Required ratio = 4 : 3

PERCENTAGE IN ALGEBRA
7.Two tailors X and Y are paid a total of Rs. 550 per week by their
employer. If X is paid 120 percent of the sum paid to Y, how
much is Y paid per week?
A.Rs. 200 B. Rs. 250 C.Rs. 300 D.None of these
Let the sum paid to Y per week be Rs. z.
Then, z + 120% of z = 550.
𝑧 +
120
100
𝑧 = 550.
220
100
𝑧 = 550.
Z = 550X
100
220
=250.
02-03-2015
26

8.Gauri went to the stationers and bought things worth Rs. 25,
out of which 30 paise went on sales tax on taxable purchases. If
the tax rate was 6%, then what was the cost of the tax free
items?
A. Rs. 15 B. Rs. 15.70 C. Rs. 19.70 D. Rs. 20
6% of taxable =
30
100
.
Cost of taxable =
30
100
𝑋
100
6
=5.
Cost of tax free items = 25 – 5 = Rs.20.
02-03-2015
27

12.Two students appeared at an examination. One of them
secured 9 marks more than the other and his marks was 56% of
the sum of their marks. The marks obtained by them are:
A. 39, 30 B.41, 32 C. 42, 33 D.43, 34
One student secured 44% of the sum of marks.
Second student secured 56% of the sum of marks.
Difference = 12% of the sum of marks = 9 marks.
Sum of marks =
100
12
𝑋9=75.
Hence first scored
44
100
𝑋75=33 and second scored = 42.
02-03-2015
28

PERCENTAGE IN RACES & GAMES
11.A batsman scored 110 runs which included 3
boundaries and 8 sixes. What percent of his total score
did he make by running between the wickets?
A. 45% B.45
5
11
% C.54
6
11
% D.55%
Total runs not by running = 3x4 + 8x6 = 12+48=60.
Percent of his total score he made by running =
60
110
𝑋100 = 54
6
11
%
02-03-2015
29

13.A fruit seller had some apples. He sells 40% apples
and still has 420 apples. Originally, he had:
A. 588 apples B. 600 apples
C. 672 apples D. 700 apples
60% of apples = 420.
Originally he had =
100
60
𝑋420
=700 apples.
02-03-2015
30

PERCENTAGE IN NUMBER SYSTEM
14.What percentage of numbers from 1 to 70 have 1 or 9 in the
unit's digit? A.1 B.14 C.20 D.21
numbers from 1 to 70 that have 1 or 9 in the unit's digit are
1, 9, 11, 19, 21, 29, 31, 39, 41, 49, 51, 59, 61, 69.
Number of such number =14
Required percentage =
14
70
X100
=20%
02-03-2015
31

PERCENTAGE IN NUMBER SYSTEM
15.If A = x% of y and B = y% of x, then which of the following is true?
A. A is smaller than B. B. Relationship between A and B cannot be determined.
C. A is greater than B D. If x is smaller than y, then A is greater than B.
E. None of these
A = x% of y
02-03-2015
32
=
𝑥
100
𝑋𝑦 =
𝑥𝑦
100
=
𝑦𝑥
100
=
𝑦
100
𝑋𝑥 = y% of x
= B.

PROFIT & LOSS
C.S.VEERARAGAVAN
02-03-2015
33

02-03-2015
34

02-03-2015
35

Profit & Loss
There are two shopkeepers having shops
side by side.
The first shopkeeper sells bicycles.
He sells a bicycle worth $30 for $45.
One day a customer comes and buys a
bicycle.
He gives a $50 note to the shopkeeper.
The shopkeeper doesn't have change so he
goes to the second shopkeeper, gets the
change for $50, and gives $5 and the
bicycle to the customer.
The customer goes away.
The next day the second shopkeeper comes
and tells the first shopkeeper that the $50
note is counterfeit and takes his $50 back.
Now, how much does the first shopkeeper
lose?
02-03-2015
36
From the second shopkeeper he took
$50 and gave back $50 so there was no
profit no loss. To the customer he gave
$5 + $30 bicycle. Therefore, his total
loss is $35

PROFIT / LOSS
If a man purchase 11 orange for
Rs 10 and sell them 10 for Rs
11. How much profit or loss did
he made?
Profit or loss made =
11𝑋11−10𝑋10
10𝑋10
X100 =21% profit.
If 'a' articles are bought for Rs
'b' and sell them 'c' for Rs 'd'.
Then profit or loss made by the
vendor:
𝑎𝑑 − 𝑏𝑐
𝑏𝑐
𝑥100
02-03-2015
37
USUAL METHOD
C.P of 11 oranges Rs.10
C.P of 1 orange is Rs.
10
11
.
S.P of 10 oranges Rs.11
S.P of 1 orange is Rs.
11
10
Profit or loss made
=
𝑆.𝑃 −𝐶.𝑃
𝐶.𝑃
𝑋 100
=
11
10
−
10
11
10
11
𝑋 100
=
11𝑋11 −10𝑋10
110
𝑋
11
10
𝑋100
=
11𝑋11−10𝑋10
10𝑋10
𝑋100

Example 2
A boy buys orange 9 for
Rs. 16 and sell them 11
for Rs. 20. Find profit or
loss percentage.
profit or loss percent
made :
9𝑋20−11𝑋16
11𝑋16
𝑥100 =
25
11
% 𝑝𝑟𝑜𝑓𝑖𝑡
02-03-2015
38
Did the original problem
really have so much
information in it ?
Yeeeeesssssss ---
only if you go down
deep enough.
It is IMPOSSIBLE to get
to solutions like these, if
you tend to rush through
to the solution using the
most familiar ways
known to you.

PROFIT PERCENTAGE
Some articles were bought at 6 articles for Rs. 5
and sold at 5 articles for Rs. 6. Gain percent is:
A. 30% B. 33
1
3
% C. 35% D. 44%
Gain % =
36−25
25
𝑥100 = 44%
02-03-2015
39

PROFIT PERCENTAGE
A shopkeeper expects a gain of 22.5% on his cost price.
If in a week, his sale was of Rs. 392, what was his
profit?
A. Rs. 18.20 B. Rs. 70
C. Rs. 72 D. Rs. 88.25
C.P =
100
122.5
x392 = Rs.320.
Profit = Rs.392 – Rs.320 = Rs.72.
02-03-2015
40

PROFIT PERCENTAGE
Sam purchased 20 dozens of toys at the rate of Rs. 375 per
dozen.
He sold each one of them at the rate of Rs. 33.
What was his percentage profit?
A.3.5 B.4.5 C.5.6 D.6.5
C.P of 1 toy =
375
12
= 31.25
S.P = 33.
Profit % =
33 −31.25
31.25
x100
=
1.75
31.25
x100 = 5.6%
02-03-2015
41
C.P = Rs.375 per dozen
S.P = 33 x 12 = Rs.396
Profit % =
396 −375
375
x100
=
21
375
x 100
=
28
5

PROFIT PERCENTAGE
Alfred buys an old scooter for Rs. 4700 and spends Rs.
800 on its repairs.
If he sells the scooter for Rs. 5800, his gain percent is:
A. 4
4
7
% B. 5
5
11
% C.10% D. 12%
Cost Price (C.P.) = Rs. (4700 + 800) = Rs. 5500.
Selling Price (S.P.) = Rs. 5800.
Gain = (S.P.) - (C.P.) = Rs.(5800 - 5500) = Rs. 300.
Gain% =
300
5500
𝑋100 = 5
5
11
%
02-03-2015
42

PROFIT PERCENTAGE
If selling price is doubled, the profit triples.
Find the profit percent.
A.66
2
3
B. 100 C. 105
1
3
D. 120
Let C.P be x . S.P = y. Profit = y – x .
Given 3(y – x) = 2y – x.
Y = 2x.
Profit % =
y−x
x
𝑋 100=
x
x
𝑋100= 100.
02-03-2015
43

PROFIT PERCENTAGE
In a certain store, the profit is 320% of the cost. If the
cost increases by 25% but the selling price remains
constant, approximately what percentage of the selling
price is the profit?
A.30% B. 70% C.100% D. 250%
Let C.P.= Rs. 100. Then, Profit = Rs. 320, S.P. = Rs. 420.
New C.P. = 125% of Rs. 100 = Rs. 125
New S.P. = Rs. 420.
Profit = Rs. (420 - 125) = Rs. 295.
Profit % =
295
420
x100 =
59
84
x100 ≈
60
84
x100 =
500
7
= 70%.
02-03-2015
44

Percentage and profit loss new version 4

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