Maths, working out the unknown

Question

Hello, I would like to know how to solve such problems:

 

'Fred is making two rectangular flower beds.

The dimensions of the larger rectangle will be three times the dimensions of the smaller rectangle.

 

There is going to be the same depth of soil in each flower bed.

Fred needs 180kg off soil for the smaller flower bed.

 

Work out how much soil Fred needs for the larger flower bed.'

 

Thank you in advance.

Answer 1

The comment of Tom from Belleville, MI on Dec. 27 is the correct answer. The key idea is that the amount of soil needed in each rectangle is proportional to the area of the rectangle. Since the larger rectangle has 9x more area, it needs 9x more soil.