In One Fortnight Of A Given Month, There Was A Rainfall Of 10 CM

In One Fortnight Of A Given Month, There Was A Rainfall Of 10 CM In A River Valley. If The Area Of The Valley Is 97280KM Show That The Total Rainfall Was Approximately Equal To The Addition To The Normal Water Of Three Rivers Each 1072 Km ,75 KM Wide And 3M Deep.

Please note that there is an error in the question. The area of the valley will be 7280 km2 and not 92780 km2 and also the breadth of the river will be 75m instead of 75 km
So, then using simple volume formulas for cuboid, where volume = l × b × h or area × h
The volume of rainfall in the area = 7280 ×10 × 0.00001 km3 = 0.728 km3
Volume of water in 3 rivers = 3 ×1072 × 75 × 0.001 × 3 × 0.001 km3 = 0.723 km3
Hence, the 2 values are nearly similar.