Question

If the base of a rectangle is increased by 30% and the altitude is decreased by 20%the area is increased by?

Answer 1

The new area is 104% of the old, an increase of 104% - 100% = 4%.

Answer 2

can you explain the steps

Answer 3

Call the original base b and the original altitude a. The area A of the rectangle is A = ab.

If the base then grows by 30%, it's new value is 1.3b. If the altitude decreases by 20%, the new altitude is 0.8a. The new area is therefore A = (0.8a)(1.3b) = 1.04ab.

You can see therefore that the new area is 1.04 times the value of the old area, meaning it has increased by 4%.