Three sound sources `A`, `B` and `C` have frequencies `400`, `401` and `402 H_(Z)`, respectively. Cacluated the number of beats noted per second.

Explanation

To calculate the number of beats noted per second from the three sound sources with frequencies 400 Hz, 401 Hz, and 402 Hz, we can follow these steps:

### Step 1: Identify the Frequencies
We have three sound sources:
- Frequency of A (f_A) = 400 Hz
- Frequency of B (f_B) = 401 Hz
- Frequency of C (f_C) = 402 Hz

### Step 2: Determine the Beat Frequencies
The beat frequency is calculated as the absolute difference between the frequencies of two sound sources. We will calculate the beat frequencies for each pair of sources.

1. Beats between A and B:
\[ f_{AB} = |f_A - f_B| = |400 - 401| = 1 \text{ Hz} \]

2. Beats between B and C:
\[ f_{BC} = |f_B - f_C| = |401 - 402| = 1 \text{ Hz} \]

3. Beats between A and C:
\[ f_{AC} = |f_A - f_C| = |400 - 402| = 2 \text{ Hz} \]

### Step 3: Calculate the Total Number of Beats
The total number of beats per second is the sum of the beats from each pair:
\[ \text{Total Beats} = f_{AB} + f_{BC} + f_{AC} = 1 + 1 + 2 = 4 \text{ Hz} \]

### Final Answer
The number of beats noted per second is **4 Hz**.

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