Question 57

A towel, when bleached, was found to have lost 20% of its length and 10% of its breadth. Find the percentage of decrease in its area.

Solution

initial length = 100

initial breadth = 100

area = $$ 100 \times 100 = 10000 $$

new length = $$ 100 \times \frac{80}{100} = 80 $$

new breadth = $$ 100 \times \frac{90}{100} = 90 $$

new area = $$ 80 \times 90 = 7200 $$

change in area = 10000 - 7200 = 2800

percentage of decrease in its area = $$ \frac{2800}{10000} \times 100 = 28 $$%

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