If the sides of a square are decreased by 20%, find the percentage change in its area.
यदि एक वर्ग की भुजा की लम्बाई 20% कम कर दी जाय, तो उसके क्षेत्रफल में होने वाले परिवर्तन का प्रतिशत ज्ञात करें।
A
40%
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B
36%
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C
20%
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D
30%
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Solution
The correct option is B 36% Let the side of the square be ‘x’. Area of the square = x2 Area of the new square = 0.8x × 0.8x = 0.64x2 Hence, the percentage change = x2−0.64x2x2×100=36%
माना कि वर्ष की भुजा ‘x’ है। वर्ग का क्षेत्रफल = x2 नए वर्ग का क्षेत्रफल = 0.8x × 0.8x = 0.64x2 अत: प्रतिशत परिवर्तन = x2−0.64x2x2×100=36%