The area between the isohyets 45 cm and 55 cm is 100 square km and between 55 cm and 65 cm is 150 square km. The average depth of annua! precipitation over the above basin of 250 square km will be

first taking average = 45 + 55/ 2 = 50cm
65 + 55 / 2 = 60cm
Precipitation for the area of 100 square km between 45 cm and 55 cm and 150 square km between 55 cm and 65 cm
total rainfall = average * 100 = 50 * 100 = 5000 cm. km sqa and also total rainfall = 60 * 150 = 9000 cm. km sqa
total area = 250 km sqa
total rainfall = 9000 + 5000 = 14000 km sq. cm
average depth = total precipitation / Area = 14000 / 250 = 56cm

First of all take a average of areas given
45+55/2 =50
55+65/2 = 60
(50×100)+(60×150)/250 = 56cm

[(50*100) + (60*150)]/250 = 56 cm

Pls explain