Discussion

Question:

If the length and breadth of a rectangle are decreased by 20%, then by what percent does the area decrease?

Explanation:

Let Length and Breadth be L and B respectively. So area = LB

Length becomes 0.8 L

Breadth become 0.8 B

New Area = 0.8 L × 0.8B = 0.64 LB

Percentage decrease in area = $\frac{L B - 0.64 L B}{L B}$ × 100 = 36%.

Alternately,

Net change = -20 -20 + $\frac{- 20 \times - 20}{100}$ = -36%

Hence, option (d).

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