If his heartbeat has increased by 8 beats per minute after 20 minutes of working out how much will his heartbeat have increased after 30 minutes of working out

12 beats per minute after 30minutes

Step-by-step explanation:

Since we are told by how much his heartrate increased in 20 minutes, we can simply calculate how much it increased in 10 minutes and add that amount to the current heart rate to know how much his heartrate increased after 30 minutes of working out. Since 10minutes would be half of the 20minutes we simply divide the beats per minute by 2.

8 / 2 = 4 beats per minute after 10 minutes

Now we simply add this to the beats per minute at the 20minute mark to calculate the beats per minute at 30minutes

8 + 4 = 12 beats per minute after 30minutes

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step-by-step explanation: