NCERT Solutions for Class 10 Maths Chapter 13

Important NCERT Questions

Surface areas and Volumes,

NCERT Books for Session 2022-2023

CBSE Board and UP Board Others state Board

EXERCISE 13.5

Page No:258

Questions No:3

# A cistern, internally measuring 150 cm × 120 cm × 110 cm, has 129600 cm3 of water in it. Porous bricks are placed in the water until the cistern is full to the brim. Each brick absorbs one-seventeenth of its own volume of water. How many bricks can be put in without overflowing the water, each brick being 22.5 cm × 7.5 cm × 6.5 cm?

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Volume of cistern = 150 × 120 × 110 = 1980000 cm³

Volume of water in cistern = 129600 cm³

Volume of bricks to be filled in cistern = 1980000 – 129600 = 1850400 cm³

Let, the number of bricks = n

Therefore, Volume of n bricks = n × 22.5 × 7.5 × 6.5 = 1096.875 n

As each brick absorbs 1/17 of its volume, therefore, the volume of water obsorbed by n bricks = n/17 × 1096.875

According to question,

18504000 + n/17 × 1096.875 = 1096.875n

⇒ 18504000 = 16n/17 × 1096.875n ⇒ n = 1792.41

Hence, 1792 bricks can be put into the cistern without overflow the water.