self Maths Puzzle

5.
A hollow iron pipe is 21 cm long and its external diameter is 8 cm. If the thickness of the pipe is 1 cm and iron weighs 8 g/cm3, then the weight of the pipe is:

A. 3.6 kg B. 3.696 kg
C. 36 kg D. 36.9 kg

Read Solution (Total 1)

External radius = 4 cm
Internal radius = 3 cm [because thickness of pipe is 1 cm]

Volume of iron =πr2h=227∗[42−32]∗21cm3=227∗1∗21cm3=462cm3
Volume of iron =πr2h=227∗[42−32]∗21cm3=227∗1∗21cm3=462cm3

Weight of iron = 462*8 = 3696 gm
= 3.696 kg
8 years agoHelpfull: Yes(0) No(0)

self Other Question

A hall is 15 m long and 12 m broad. If the sum of the areas of the floor and the ceiling is equal to the sum of the areas of four walls, the volume of the hall is:

A. 720 B. 900
C. 1200 D. 1800
50 men took a dip in a water tank 40 m long and 20 m broad on a religious day. If the average displacement of water by a man is 4 m3, then the rise in the water level in the tank will be:

A. 20 cm B. 25 cm
C. 35 cm D. 50 cm