Paper 1 · Mathematical Reasoning and Aptitude
If the length of a rectangle increases by 10%, by what percentage should the breadth decrease to keep the area the same?
A10
B20
C9.11 ✓ Correct
D5
Correct answer: (C) 9.11 — The breadth should decrease by about 9.11%, so that is the answer.
Explanation
★The breadth should decrease by about 9.11%, so that is the answer.
★The area is length times breadth and must stay the same.
★The length becomes 1.1 times the old length after a 10 per cent rise.
★So the breadth must become 1 divided by 1.1 of the old breadth.
★1 divided by 1.1 is about 0.9091, a fall of about 0.0909.
★So the breadth should decrease by about 9.11 per cent.
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