Question

8. How long will a man take to make a round of a circular field of radius 21 m, cycling
speed of 8 km/h?
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Answer 1

Time =distance /speed

$time = \frac{2\pi \: r}{8} \\ = 42 \times \pi \times \frac{1}{8} \\ = 6\pi \\ = 18.8 \: hrs$

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Answer 2

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Answer:

The time taken by the man who cycling at the speed of 8km/h on circular field is 59.4 seconds .

Step-by-step explanation:

Formula

$Circumference\ of\ a\ circle = 2\pi r$

Where r is the radius of the circle .

$Speed = \frac{Distance}{Time}$

As given

A man take to make a of a circular field of radius 21 m.cycling at the speed of 8km/h .

Put all the values in the formula

$\pi =\frac{22}{7}$

$Circumference\ of\ a\ circle = 2\times \frac{22}{7}\times 21$

$Circumference\ of\ a\ circle = 2\times 22\times 3$

$Circumference\ of\ a\ circle = 132\ m$

As 1 km = 1000 m

$1\ m = \frac{1}{1000}\ km$

Now convert 132m into km .

$132\ m = \frac{132}{1000}\ km$

                  = 0.132 km

I.e

Distance = 0.132 km

Speed = 8 km / h

Put all the values in the formula

$8 = \frac{0.132}{Time}$

$Time= \frac{0.132}{8}$

Time = 0.0165 hr

As

1 hour = 3600 second

Now convert  0.0165 hr into seconds .

0.0165 hour = 0.0165 × 3600

                      = 59.4 seconds

Therefore the time taken by the man who cycling at the speed of 8km/h on circular field is 59.4 seconds .

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