Question

solve the attachment

Answer 1

$\mathbb{\pink{\huge{HELLO}}}$

depth=12dm=1.2m
width=30dm=3

Flow velocity =20km/h=20,000m/s
time =30min =0.5h
standing water required =9cm-0.09m
let the area =Am^2
volume of water will be same
1.2m×3m×20,000m/h×0.5h
A=0.09
A=36,000/0.09
A=4,00,000

Answer 2

See the attachment..........