एक लम्ब वृत्तीय बेलन का वक्र पृष्ठीय क्षेत्रफल 616 cm2 है और इसके आधार का क्षेत्रफल 38.5 cm2 है। बेलन का आयतन (cm3 में) कितना है? (π = का प्रयोग कीजिए)

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RRB Technician Grade III Official Paper (Held On: 30 Dec, 2024 Shift 2)
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  1. 1078
  2. 1155
  3. 1408
  4. 1243

Answer (Detailed Solution Below)

Option 1 : 1078
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दिया गया है:

एक लम्ब वृत्तीय बेलन का वक्र पृष्ठीय क्षेत्रफल 616 cm2 है।

इसके आधार का क्षेत्रफल 38.5 cm2 है।

प्रयुक्त सूत्र:

वक्र पृष्ठीय क्षेत्रफल (CSA) = 2πrh

आधार का क्षेत्रफल = πr2

आयतन = πr2h

गणना:

CSA = 616 cm2

⇒ 2πrh = 616

⇒ 2 × (22/7) × r × h = 616

⇒ rh = 616 × 7 / 44 = 98

आधार का क्षेत्रफल = 38.5 cm2

⇒ πr2 = 38.5

⇒ (22/7) × r2 = 38.5

⇒ r2 = 12.25

⇒ r = √12.25 = 3.5 cm

अब, rh = 98

⇒ 3.5h = 98

⇒ h = 28 cm

आयतन = πr2h

⇒ आयतन = (22/7) × (3.5)2 × 28

⇒ आयतन = (22/7) × 12.25 × 28

⇒ आयतन = 1078 cm3

∴ सही उत्तर विकल्प 1 है।

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