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प्रश्न
The circumference of a circle is equal to the sum of the circumference of two circles having diameters 36 cm and 20 cm. The radius of the new circle is
विकल्प
16 cm
28 cm
42 cm
56 cm
उत्तर
28 cm
Let r cm be the radius of the new circle.
We know:
Circumference of the new circle = Circumference of the circle with diameter 36 cm + Circumference of the circle with diameter 20 cm
Thus, we have:
2πr = 2πr + 2πr2
⇒ 2πr = (2π × 18) + (2π × 10)
⇒ 2πr = 2π × (18 + 10)
⇒ 2πr = (2πr × 28 )
`⇒ 2πr =( 2 × 22/7xx28)`
⇒ 2πr = 176
`⇒ 2 × 22/7xx"r"=176`
`=> "r" = (176xx7/44)`
⇒ r =28 cm
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