Question

The total weight of 15 boxes is 45 pounds .how much would 40 boxes weigh

Answer 1

40 boxes would weigh would weigh 120 pounds

Answer 2

To answer this, we must first assume that each box weighs the same.  If this is true, you would make a rate of how many pounds in 15 boxes: 45 lbs/15 boxes.  From here determine the weight per box by dividing 45 by 15.  This means each box is 3 pounds.  Multiply this by the total number of boxes (3 x 40).  This gives you a total weight of 120 pounds for 40 boxes.