The daily minimum temperature of a place in a certain week, beginning from Monday was `20^@`, `18.6^@`, `17^@`,`21.4^@`,`19^@` and `19.8^@`.It was known that the average of the whole week was `19.5^@` .The minimum temperature on Sunday was

Answer

To find the minimum temperature on Sunday, we can follow these steps:

### Step 1: List the temperatures from Monday to Saturday
The temperatures for the week from Monday to Saturday are:
- Monday: 20°C
- Tuesday: 18.6°C
- Wednesday: 17°C
- Thursday: 21.4°C
- Friday: 19°C
- Saturday: 19.8°C

### Step 2: Calculate the total temperature for Monday to Saturday
Now, we will sum these temperatures:
\[ \text{Total from Monday to Saturday} = 20 + 18.6 + 17 + 21.4 + 19 + 19.8 \]
Calculating this gives:
\[ 20 + 18.6 = 38.6 \]
\[ 38.6 + 17 = 55.6 \]
\[ 55.6 + 21.4 = 77 \]
\[ 77 + 19 = 96 \]
\[ 96 + 19.8 = 115.8 \]
So, the total temperature from Monday to Saturday is **115.8°C**.

### Step 3: Set up the equation for the average temperature
We know that the average temperature for the whole week (7 days) is 19.5°C. The average is calculated by dividing the total temperature by the number of days:
\[ \text{Average} = \frac{\text{Total Temperature}}{\text{Number of Days}} \]
Let \( x \) be the temperature on Sunday. Therefore, the total temperature for the week (including Sunday) is:
\[ 115.8 + x \]
The equation for the average becomes:
\[ 19.5 = \frac{115.8 + x}{7} \]

### Step 4: Multiply both sides by 7 to eliminate the fraction
\[ 19.5 \times 7 = 115.8 + x \]
Calculating \( 19.5 \times 7 \):
\[ 19.5 \times 7 = 136.5 \]
So we have:
\[ 136.5 = 115.8 + x \]

### Step 5: Solve for \( x \)
To find \( x \), we subtract 115.8 from both sides:
\[ x = 136.5 - 115.8 \]
Calculating this gives:
\[ x = 20.7 \]

### Conclusion
The minimum temperature on Sunday is **20.7°C**.

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