Question

A boat having a length 3 m and breadth 2 m is floating on a lake. The boat sinks by 1 cm when a man gets on it. The mass of the man is:

Answer 1

L=3m, B= 2m, h=1cm= .01m

Vol of water displaced= 3 × 2×.01
vol of water displaced = 0.06m^3

mass = vol × density

density of water= 1000 kg/m^3

mass of man = 0.06 × 1000
mass of man = 60 kg

Answer 2

Given,
length =3 m
breadth =2 m 
height=1cm = 0.01m
And it is said the boat sinks by 1 cm when a man gets on it
Acc,
volume of water that is displaced= (3*2*0.01) m³
                                                    = 0.06 m³
mass of the man=density of water*volume of water displaced

we got walume of the water displaced to be = 0.06 m³
density of water= 1000 kg/m³
∴mass of man=(0.06 × 1000)kg
                       =60 kg