Original: 45

New: 50

Since the new amount is greater than the original, this is a percent of increase.

The amount of change = New Amount – Original Amount.

The amount of change = .

Let r be the percentage of increase.

Use the original number, 72 as the base.

The percent proportion is

To solve for r, first find the cross products.

                                    (Multiply: )

                              (Divide each side by 72)

                                       (Cancel common terms)

                                             (Divide: )

The percentage of increase by 50%

The percent of change is a percent of increase.

The percentage of increase by 50%.