Question

A tank is 25 m long, 12 m wide and 6 m deep. The cost of plastering its walls and bottom at 75 paise per sq. m, is:

Answer 1

u can solve it by long wall short wall method

1) inner plastering

long wall (25m)
L = 25
H = 6m
no. of plastering = 2 ( in a tank, 2 walls of same length( rectangle tank))
plastering = 25*6*4
= 600 square meter

similarly , short wall (12m)
L = 12m
B= 6m
plastering = 12*6*2
=144 square meter

2) outer plastering
here we include, thickness of wall
long wall (25m)
L=25m
H=6m
wall thickness = 0.9m
no. of plastering = 2 ( because, 2 identical walls)
plastering = 25×(2×.9)
=22.5 square meter

similarly, short wall
plastering = 12×(2×.9)
= 10.8 squaremeter

3) bottom portion
L = 25m
B= 12m
plastering = 25×12
= 300 square meter

cost for plastering
total no. of plastering ( 600+144+22.5+10.8+300)
coast of plastering = 75 paise per Sq. m

= 1080×75 paise
= 8100 paise
= Rs. 810


i hope it's helpful