Question

The radius of a wheel of a cycle is 70cm and it takes 5 minutes to make 300 rotations. Find the speed of the cycle in km/hr.
$take \frac{22}{7} (\pi)$
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Answer 1

Given , radius = 70cm

for 300 rotations it takes 5minuts

The circumference

$2\pi \: r = 2 \times 3.14 \times 70 \\ \\ \: \: = 6.28 \times 70 \\ \\ \\ \\ now \: distance \: covered \: is \: \\ \\ = 300 \times 6.28 \times 70m \\ \\ = 2700 \times 6.28 m \\ \\ = \frac{27 \times 100 \times 6.28}{1000} km \\ \\ = 27 \times .628km\\ \\ now \: 6minute = \frac{6}{60} h \\ \\ = \frac{1}{10} h \\ \\ = 0.1h \\ \\ so \: speed \: = \frac{d}{t} \\ \\ = \frac{27 \times 0.628}{0.1} \\ \\ = 27 \times 0.628 \times 10 \\ \\ = 27 \times 6.28$

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