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Surface Areas and Volumes
Question
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The radii of two circles are 19 cm and 9 cm respectively. Find the radius of the circle which has circumference equal to the sum of the circumference of two circles.

Answer

Let the radius of the bigger circle be R cm. and radii of two smaller circles are r1and r2, then according to question.
2πR = 2πr1 + 2πr2
⇒    2πR = 2π (19) + 2π (9)
⇒    2πR = 2π (19 + 9)
⇒    R = 28
Hence, radius of the circle be 28 cm.

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Some More Questions From Surface Areas and Volumes Chapter

The wheels of a car are of diameter 80 cm each. How many complete revolutions does each wheel make in 10 minutes when the car is travelling at a speed of 66 km per hour?

Tick the correct answer in the following: If the perimeter and the area of a circle are numerically equal, then the radius of the circle is
(A) 2 units    (D) π units
(C) 4 units    (D) 7 units.