RRB Group D practice question
The side of a square is increased by 10%. Find the percentage increase in its area.
From a RRB Group D Quantitative Aptitude practice set · Quantitative Aptitude
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Correct answer: (A) 21%
Let the original side of the square be a. New side = a(1 + 10/100) = 1.10a (factor). Original area = a2. New area = [a(1+10/100)]2 = a2 × (1.1000)2 = a2 × 1.2100. So the percentage change in area = [(1+10/100)2 - 1] × 100 = 21%. Since the factor is greater than 1, the area increases by 21%.
हिंदी में प्रश्न
एक वर्ग की भुजा में 10% की वृद्धि की जाती है। इसके क्षेत्रफल में प्रतिशत वृद्धि ज्ञात कीजिए।
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सही उत्तर: (A) 21%
माना वर्ग की मूल भुजा a है। नई भुजा = a(1 + 10/100)। मूल क्षेत्रफल = a², नया क्षेत्रफल = a² × (1+10/100)² = a² × 1.2100। अतः क्षेत्रफल में प्रतिशत परिवर्तन = [(1+10/100)² - 1] × 100 = 21%। चूँकि गुणांक 1 से अधिक है, इसलिए क्षेत्रफल में 21% की वृद्धि होगी।
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