Question

Water in a canal $4m$ wide and $1.5m$ deep is flowing with velocity $12$ km per hour. How much area will it irrigate in $30$ minutes, if $9cm$ of standing water is required for irrigation?

• A. $220000m^2$
• B. $400000m^2$
• C. $580000m^2$
• D. $800000m^2$

Answer 1

The correct option is B $400000m^2$

Width of canal$=4m$,

depth$=1.5m$,

Velocity of water$=12km/hr$, time$=30$min$=30\times 60$sec $=1800$sec

So distance covered by water $=$ velocity $\times$ time $=\frac{1800\times 12\times 1000}{3600}=6000$ m,

Volume$=lbh$

$V=6000\times 1.5\times 4$

$V=36000m^3$

Area irrigated if $9cm=0.09m$ of standing water is required for irrigation.

$A=\frac{V}{\text{Height of standing water}}$$=\frac{36000}{0.09}$$=400000m^2$