Question

Water in a canal, $30dm$ wide and $12dm$ deep is flowing with a speed of $20km$ per hour. How much area will it irrigate in $30min$ if $9cm$ of standing water is desired? ($10dm=1m)$

Answer 1

Given width of the canal $=30$dm $=300$ cm

Depth of canal $=12$ dm $=120$ cm

Rate of flow of water $=20$ kmphr

Distance covered by the water that will flow in $30$ minutes

$=1000000$ cm

Amount of water irrigated in $30$ minutes $=300\times 120\times 1000000$

$=36000000000$ cu cm

Area irrigated if $9$ cm standing water is desired $=\left(\frac{36000000000}{9}\right)$

$=4000000000$ sq cm

$=0.4$ sq km