Percentage
Q31. If the price of sugar falls by 5%, by how much percent must a house holder increase its consumption, so as not to decrease its expenditure on sugar ?
(a) 3 3/19 %
(b) 5 5/19 %
(c) 7 7/19 %
(d) 9 9/19 %
Answer: (b) 5 5/19 %
Increase % in consumption = { | R | X 100 } % |
100 - R |
= | 5 | X 100 % |
100 - 5 |
= | 5 | X 100 % |
95 |
= | 100 | % |
19 |
= 5 | 5 | % |
19 |
Q32. If 10% of A = 20% of B = 1/5 of C, then A:B:C is
(a) 2:1:1
(b) 1:2:1
(c) 1:1:2
(d) 1:2:2
Answer: (a) 2:1:1
10% of A = 20% of B = 1/5 of C
⇒ | 10 | X A = | 20 | X B = | 1 | X C |
100 | 100 | 5 |
⇒ | A | = | B | = | C |
10 | 5 | 5 |
⇒ | A | = | B | = | C |
2 | 1 | 1 |
∴ A:B:C = 2 : 1 : 1
Q33. 4 liters of water is added to 20 liters of a mixture of a 40% solution of alcohol in water. The strength of alcohol is now ?
(a) 23 1/3 %
(b) 27 1/3 %
(c) 33 1/3 %
(d) 37 1/3 %
Answer: (c) 33 1/3 %
Alcohol in 20 liters of mixture = | 40 | X 20 liters = 8 liters |
100 |
Now, alcohol in 24 liters of mix = 8 liters
∴ Strength of alcohol = | 8 | X 100 % |
24 |
= 33 | 1 | % |
3 |
Q34. By how much is 30% of 80 greater than 56 of 24 ?
(a) 3
(b) 4
(c) 5
(d) 7
Answer: (b) 4
30% of 80 = | 30 | X 80 = 24 |
100 |
5 | of 24 = | 5 | X 24 = 20 |
6 | 6 |
Required no = 24 - 20 = 4
Q35. x % of y is y % of ?
(a) x
(b) xy
(c) xy2
(d) x2
Answer: (a) x
x % of y = | x | X y = | xy |
100 | 100 |
Now y% of ? = | xy |
100 |
⇒ | y | X ? = | xy |
100 | 100 |
⇒ ? = | xy | X | 100 | = x |
100 | y |
Q36. When a number is first increased by 10% and then reduced by 10% the number
(a) 1%
(b) 2%
(c) 5%
(d) 10%
Answer: (a) 1%
Let the number be x
After increasing, the new number be = x + x X 10%
= x + | 10x |
100 |
= | 11x |
10 |
Reducing by the new number by 10% = | 11x | - | 11x | X 10 % |
10 | 10 |
= | 11x | - | 11x | X | 10 |
10 | 10 | 100 |
= | 11x | - | 11x |
10 | 100 |
= | 110x - 11x |
100 |
= | 99x |
100 |
Decrease = (x - | 99x | ) = | x |
100 | 100 |
Decrease %= | x/100 | X 100% |
x |
= | x | X 100% = 1 % |
100x |
Q37. What is 30% of 30% equal to ?
(a) 0.06
(b) 0.09
(c) 0.12
(d) 0.15
Answer: (b) 0.09
Let the number be x
∴ x = 30% of 30%
= | 30 | X | 30 |
100 | 100 |
= | 9 |
100 |
= 0.09
Q38. If the side of a square is decreased by 10% then its area is decreased by ?
(a) 10%
(b) 12%
(c) 16%
(d) 19%
Answer: (d) 19%
Let the side of a square be x
∴ Area of the square = x X x = x2
After decreasing
side of the square be = x - x X 10 % = x - 10x/100 = 9x/10
∴ Area of the new square = | 9x | X | 9x | = | 81x2 |
10 | 10 | 100 |
∴ Decrease in Area = x2 - | 81x2 | = | 19x2 |
100 | 100 |
∴ Decrease % = | 19x2/100 | X 100 % |
x2 |
= | 19x2 | X 100 % |
100x2 |
= 19 %
Q39. Which number is 40% less than 70 ?
(a) 49
(b) 46
(c) 45
(d) 42
Answer: (d) 42
Let the required number be x
A/Q x = 70 - 70 X 40 %
= 70 - 70 X | 40 |
100 |
= 70 - 28 = 42
Q40. The price of an article has been reduced by 20%. In order to restore
(a) 49
(b) 46
(c) 45
(d) 42
Answer: (d) 42
Let the required number be x
A/Q x = 70 - 70 X 40 %
= 70 - 70 X | 40 |
100 |
= 70 - 28 = 42
Practice Test Exam