The average of three numbers be 21. If two of the numbers are 4 and 12, what is the remaining number?
1. 20
2. 30
3. 47
4. 52
1. 20
2. 30
3. 47
4. 52
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Correct Answer – Option 3 : 47
Concept:
\(\rm Mean\ of\ ‘n’\ observations=\dfrac{Sum\ of\ observations}{n}\).
Calculation:
Let’s say that the third number is x.
So, Numbers are 4, 12 and x
Here n = 3
As we know, \(\rm Mean\ of\ ‘n’\ observations=\dfrac{Sum\ of\ observations}{n}\)
∴ \(\rm 21=\dfrac{4+12+\rm x}{3}\)
⇒ x + 16 = 63
⇒ x = 47.