What is the recommended heart rate for a 20 year old person?

The average maximum heart rate for a 20 year old is 200 bpm

The target heart rate is 100-170 beats per minute (bpm).

I Hope this helps and I hope everything is okay!

The answer is 45° and 55 °.

180° - 80° = 100°

Then add the two numbers from the ratio:

9 + 11 = 20

The divide 100 from 20.

100 ÷ 20 = 5

Then multiply it to two numbers from the ratio:

9 × 5 = 45 and 11 × 5 = 55

I hope it helps.