बैडमिंटन खेलने के लिए इस्तेमाल की जाने वाली चिड़ी एक अर्धगोले पर रखे शंकु के छिन्नक के आकार का होता है। छिन्नक के व्यास 5 सेमी और 2 सेमी हैं, चिड़ी की कुल ऊँचाई 7 सेमी है। बाह्य पृष्ठीय क्षेत्रफल ज्ञात कीजिए।

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RRB ALP Previous Paper 10 (Held On: 10 Aug 2018 Shift 1)
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  1. 84.30 सेमी2
  2. 80 सेमी2
  3. 74.29 सेमी2
  4. 63.38 सेमी2

Answer (Detailed Solution Below)

Option 3 : 74.29 सेमी2
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Detailed Solution

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F2 Savita Railways 10-4-24 D1

r = 1 सेमी, R = 2.5 सेमी, h = 7 सेमी​

छिन्नक की ऊँचाई = 7 - 1 = 6 सेमी

⇒ l = √[h2 + (R – r)]2

⇒ l = √[(6)2 + (2.5 – 1)2]

⇒ l = √(36 + 2.25)

⇒ तिर्यक ऊँचाई, l = 6.2 सेमी

बाह्य पृष्ठीय क्षेत्रफल = (छिन्नक का वक्र पृष्ठीय क्षेत्रफल) + (अर्धगोले का वक्र पृष्ठीय क्षेत्रफल)

⇒ बाह्य पृष्ठीय क्षेत्रफल = 22/7 × (r + R) × l + 2 × (22/7) × r2

⇒ बाह्य पृष्ठीय क्षेत्रफल = 22/7 × [(1 + 2.5)6.2 + 2 × (1)2]

⇒ बाह्य पृष्ठीय क्षेत्रफल = 22/7 × (3.5 × 6.2 + 2)

⇒ बाह्य पृष्ठीय क्षेत्रफल = 22/7 × (21.7 + 2) = 74.29 सेमी2

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