To determine John's heart rate in beats per minute (bpm), we'll follow a clear, step-by-step process.
1. Observation: John counted 20 heartbeats in 10 seconds.
2. Convert the time to minutes: Since heart rates are typically measured in beats per minute, we need to convert the 10 seconds into minutes. There are 60 seconds in 1 minute, so:
[tex]\[
\text{time in minutes} = \frac{\text{seconds}}{60} = \frac{10 \text{ seconds}}{60} = \frac{1}{6} \text{ minutes}
\][/tex]
3. Calculate the heart rate: Heart rate (in bpm) is calculated by dividing the number of heartbeats by the time in minutes:
[tex]\[
\text{heart rate} = \frac{\text{number of heartbeats}}{\text{time in minutes}} = \frac{20 \text{ heartbeats}}{\frac{1}{6} \text{ minutes}}
\][/tex]
Simplifying this, we get:
[tex]\[
\text{heart rate} = 20 \text{ heartbeats} \times 6 = 120 \text{ bpm}
\][/tex]
Therefore, John's heart rate is [tex]\(120\)[/tex] beats per minute (bpm).
Thus, the correct answer is:
A. 120 bpm
