The average weight of 12 persons increases by 3.5 kg when a new person comes in place of one of them weighing 58 kg. The weight of the new person is:

100 kg

Lets assume weight of new man be x

Sum of weight before replacement be y

As average weight is increased by 3.5 kg

⇒ \(\frac{y - 56 + x}{12}\) = \(\frac{y}{12}\) + 3.5

⇒ y - 58 + x = y + 42

⇒ x = 100 kg