The average rainfalls in the month of january and february is 6 cm and in the month of march to june is 5 cm july to october is 10 cm and in the november and december it is 6 cm the average rainfall for the whole year is:

Options

A. 7
B. 5.5
C. 7.5
D. none of these

Answer

To find the average rainfall for the whole year based on the given monthly averages, we can follow these steps:

### Step 1: Determine the total rainfall for each period
1. **January and February**: The average rainfall is 6 cm for 2 months.
\[ \text{Total rainfall} = 6 \, \text{cm} \times 2 = 12 \, \text{cm} \]

2. **March to June**: The average rainfall is 5 cm for 4 months.
\[ \text{Total rainfall} = 5 \, \text{cm} \times 4 = 20 \, \text{cm} \]

3. **July to October**: The average rainfall is 10 cm for 4 months.
\[ \text{Total rainfall} = 10 \, \text{cm} \times 4 = 40 \, \text{cm} \]

4. **November and December**: The average rainfall is 6 cm for 2 months.
\[ \text{Total rainfall} = 6 \, \text{cm} \times 2 = 12 \, \text{cm} \]

### Step 2: Add the total rainfall for the entire year
Now, we sum up the total rainfall from all the periods calculated above:
\[ \text{Total rainfall for the year} = 12 \, \text{cm} + 20 \, \text{cm} + 40 \, \text{cm} + 12 \, \text{cm} \]
\[ = 84 \, \text{cm} \]

### Step 3: Calculate the average rainfall for the whole year
To find the average rainfall, we divide the total rainfall by the number of months in a year (12 months):
\[ \text{Average rainfall} = \frac{\text{Total rainfall}}{\text{Number of months}} = \frac{84 \, \text{cm}}{12} \]
\[ = 7 \, \text{cm} \]

### Final Answer
The average rainfall for the whole year is **7 cm**.

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