we order these data:
32 minutes------------------------3 people------------------4 walls
x--------------------------------------4 people------------------7 walls
The minutes and the people are variables inversely proportional , therefore, we multiply in parallel
32 minutes3 people=x4 people
The minutes and the walls are variables directly proportinal; therefore, we multiply cross.
32 minutes7 walls=x4 walls
Therefore:
32 minutes3 people7 walls=x4 people4 walls
x=(32 minutes3 people7 walls) / (4 people* 4 walls)
x=42 minutes.
Answer: the time will be 42 minutes.
