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CBSE Class 9 Answered

A rod 2 m in length and 1.2 cm in radius is drawn into another rod of length 72 cm. Find the radius of the new rod.
Asked by Topperlearning User | 13 Oct, 2017, 01:13: PM
answered-by-expert Expert Answer

Length of the original rod (H) = 2 m = 200 cm

Radius of the original rod (r) = 1.2 cm

Let V denote the volume of the original rod.

begin mathsize 12px style straight V space equals space πR squared straight H straight V space equals space 22 over 7 cross times 1.2 squared cross times 200 straight V space equals space 6336 over 7 space cm cubed end style

Length of the new rod (h) = 72 cm

Let radius of the new rod is R and V1 denote its volume.

Volume of the new rod = volume of the original rod

 begin mathsize 12px style straight V subscript 1 space equals space straight V πR squared cross times 72 space equals space 6336 over 7 straight R squared space equals space space fraction numerator 6336 cross times 7 over denominator 7 cross times 22 cross times 72 end fraction space straight R squared space equals space 4 space cm cubed straight R space equals space 2 space cm end style

Thus, radius of the new rod = 2 cm

Answered by | 13 Oct, 2017, 03:13: PM

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