Question

how long will a boy take to run round a square field of side 35 metres if he runs at the rate of 9 km/h

Answer 1

answer in above image

Answer 2

$Given \: side \: of \: a\:square \:field (a) = 35\:m$

$Distance \: run \: around \: the \: field (d) \\= Perimeter \: of \: the \: field \\= 4a \\= 4 \: 35 \:m \\= 140\: m$

$Speed \: of \: the \: boy (s) = 9 \: km/h \\= 9 \times \frac{1000\: m }{ 60 \times 60 \:s } \\= 9 \times \frac{ 5}{18} \: m/s\\= \frac{5}{2} \: m/s$

$Time \: taken \: to \: run \: around \: the \:field\\= \frac{Distance }{speed} \\= \frac{140\: m }{ \frac{5}{2}} \\= 140 \times \frac{2}{5} \\= 28 \times 2 \\= 58 \: seconds$

Therefore.,

$\red {Time \: taken \: to \: run \: around \: the}\\\red{ \:field} \green {= 58 \: seconds}$

•••♪