The radii of the two ends of a frustum are in the ratio 4 : 1. Its height is 21 cm and its volume is 7392 cm³. Find the LARGER radius. (Take \π = 22/7 .)

Question

Accepted Answer

16 cm. Let R = 4k and r = k. Then R^2 + r^2 + Rr = 16k^2 + k^2 + 4k^2 = 21k^2 , so V = 1/3 × 22/7 × 21 × 21k^2 = 462k^2 . Setting 462k^2 = 7392 gives k^2 = 16 , k = 4, so R = 16 cm. 4 cm is the SMALLER radius; 18 cm comes from dropping the Rr term; 32 cm is the diameter, not the radius.

The radii of the two ends of a frustum are in the ratio 4 : 1. Its height is 21 cm and its volume is $7392 cm^{3}$ . Find the LARGER radius. (Take $π = \frac{22}{7} .$ )

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More Class 10 Frustum of a Cone practice

The radii of the two ends of a frustum are in the ratio 4 : 1. Its height is 21 cm and its volume is 7392cm3. Find the LARGER radius. (Take π=722​.)

Step-by-Step Solution

Master this chapter in 30 minutes a day.

More Class 10 Frustum of a Cone practice

The radii of the two ends of a frustum are in the ratio 4 : 1. Its height is 21 cm and its volume is $7392 cm^{3}$ . Find the LARGER radius. (Take $π = \frac{22}{7} .$ )