SBI Clerk Prelims practice question
The outer radius of a circular ring is 6 cm and the area of the ring is 110 cm². What is the inner radius of the ring? (Take π = 22/7)
From a SBI Clerk Prelims Quantitative Aptitude practice set · Quantitative Aptitude
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Correct answer: (D) 1 cm
π(R² − r²) = 110 ⇒ R² − r² = 110 × 7/22 = 35 ⇒ r² = 36 − 35 = 1 ⇒ r = 1 cm. (Solving π(R − r)² = area instead gives a wrong width.)
हिंदी में प्रश्न
एक वृत्ताकार वलय की बाहरी त्रिज्या 6 सेमी और वलय का क्षेत्रफल 110 वर्ग सेमी है। वलय की भीतरी त्रिज्या कितनी है? (π = 22/7 लीजिए)
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सही उत्तर: (D) 1 सेमी
π(R² − r²) = 110 ⇒ R² − r² = 110 × 7/22 = 35 ⇒ r² = 36 − 35 = 1 ⇒ r = 1 सेमी। (इसके बजाय π(R − r)² = क्षेत्रफल हल करने पर चौड़ाई गलत आती है।)
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