Mathematical Aptitude - Ratio Proportion, Percentage and Discounting
- Option : C
- Explanation : Discount on Rs 60 = 25% of Rs 60 = Rs 15
Assume that the retailer offers a discount of Rs 15 or 4 extra mangoes.
New purchase price of 4 mangoes = Rs 15
Purchase price of one mango = 15/4 = Rs 3.75
- Option : C
- Explanation : Suppose both length and breadth are 100.
Hence, area = 100 × 100
New length = 100 + 10 m = 110
As area is to be kept same,
110 × new breadth = 100 × 100
New breadth = 100 × 100/110 = 1000/11
Decrease in breadth = 100 − 1,000/11 = 100/11 = 9.11%
As breadth was assumed to be 100, no additional calculation is required for percentage figure.
- Option : B
- Explanation : Using the formula: x + y + xy/100, net percentage increase = 20 + 40 + (20 × 40)/100 = 68%
Increased price = Rs 25 + 68% of 25 = 25 + 17 = Rs 42
Alternatively: Using the multiplier factor concept, we get the final price as 25 ×[6/5]x[7/5]=Rs 42
19. The radius of a circle has increased by 20%. By what percentage does the circumference increase?
- Option : A
- Explanation : Circumference of a circle = 2pi r. As r increase by 20%, the circumference also increases by 20%.
20. The radius of a circle has increased by 20%. By what percentage does its area increase?
- Option : B
- Explanation : Area of a circle= πr2
As r2 = r × r and as r increases by 20%, r2 increases by 20 + 20 + ( 20 x 20/100)=44%
