A person walks at the rate of $5 k m / h$ . How long will he take to go a round a square park $8$ times whose area is $900 m^{2}$ .

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Solution

Finding the side of the square
$A r e a o f s q u a r e = 900 m^{2} {(s i d e)}^{2} = 900 S i d e = \sqrt{900} S i d e = 30 m$
Now, the person walks round the square field.
$P e r i m e t e r o f s q u a r e = 4 \times s i d e P e r i m e t e r o f s q u a r e = 4 \times 30 P e r i m e t e r o f s q u a r e = 120 m$
Therefore, the length of $1$ round = $120 m$
the length of $8$ round = $8 \times 120 = 960 m$
The total length in $k m = \frac{960}{1000} = 0.96 k m (1000 m = 1 k m)$
Now we know that,
$S p e e d = \frac{d i s \tan c e}{t i m e} 5 = \frac{0.96}{t i m e} t i m e = \frac{0.96}{5} = 0.198 h r$
Converting the time into minutes.
We know that $1 h r = 60 m i n$
$∴ 0.198 h r = 0.198 \times 60 = 11.88 m i n$
Hence, the time taken to take $8$ rounds of square field will be $11.88 m i n u t e s$

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