Mathematical Aptitude - Ratio Proportion, Percentage and Discounting
21. If the side of a square is increased by 25%, then its area is increased by how much per cent?
- Option : D
- Explanation : Let side of square = 100
Area = 100 × 100 = 10,000
New side = 100 + 25 = 125
New area = 125 × 125 = 15,625
Percentage increase={(15,625 – 10,000)/10,000}× 100 = 56.25
Alternatively = x + x + x2/100 = 25 + 25 + (25 × 25/100) = 56.25%
- Option : C
- Explanation : Increased length = 20 × 11/10=22 cm
Increased breadth = 10 × 120/100=10x6/5=12cm
The new area = 22 × 12 = 264 sq. cm
As there is multiplication of two quantities in the area formula, we can use the method a + b + ab/100 to calculate the percentage increase in area also.
- Option : B
- Explanation : We can use the formula x + y + xy/100 to calculate
the net increase.
25 + 12 + (25 × 12)/100 = 40%
