Question

A tank internally measuring 150 cm × 120 cm × 100 cm has 1281600 cm³ of water in it. Porous bricks are placed in the water until the tank is full upto to its brim. Each brick absorbs one-tenth of its volume of water. How many bricks of dimensions 20 cm × 6 cm × 4 cm can be put in the tank without spilling over the water. 

(a) 1100 

(b) 1200 

(c) 1150 

(d) 1250 

(e) None of these

Answer 1

(b) 1200

Volume of a brick = 20 cm × 6 cm × 4 cm = 480 cm³. 

Water absorbed by one brick = \(\big(\frac1{10}\times480\big)\) cm³ = 48 cm³.  

Let x bricks be placed in the water. 

Then, x bricks absorb 48x cm³ of water. 

∴ Vol. of water + Volume of x bricks – Volume of absorbed water = Volume of water tank 

⇒ 1281600 + 480\(x\) – 48\(x\) = 150 x 120 x 100

⇒ 432\(x\) = 1800000 – 1281600 = 518400 ⇒ \(x\) = 1200.