Question

3 trucks were required to carry 39 tons of wood.how many trucks would be required to carry 91 tons of wood ?

Answer 1

Unitary method
3 trucks --> 39 tons
1 truck --> 13 tons
13 tons --> 1 truck
91 tons --> ??
91 = 13 * 7
or 13 tons *7 --> 1 * 7 trucks
= 7 trucks

Answer 2

3 trucks carry 39 tons of wood..
so, 1 truck would carry 39/3 tons of wood I. e. 13 tons..
so, 1 ton wood will be carried by 1/13 trucks..

Therefore, for 91 tons of wood 1*91/13 trucks are required..

or, 7 trucks would be required..