Joanna ran a mile in physical education class. after resting for one hour, her heart rate was 60 beats per minute. if her heart rate decreased by 2/5, what was her heart rate immediately after she ran the mile?

So, if 60 beats was decreased by 2/5 before, we know that 60 beats = 3/5 of her heart rate after she ran the mile.

(Because 1 - 2/5 = 3/5)

So, 3/5 = 60, and we're trying to find 1.

So I would first divide both sides by 3.

3/5 = 60
/3      /3

1/5 = 20

Then multiply both sides by 5.

1/5 * 5 = 20 * 5

1 = 100

So her heart rate was 100 beats per minute immediately after she ran the mile.