A die is cast 9 times and the sum of all the observations (the observation being the number on the top face of the die) obtained till that point is 45. What should the next number be so that the average is 5?

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Solution

The correct option is B 5
We know,
$A v e r a g e = \frac{S u m o f a l l o b s e r v a t i o n s}{T o t a l n u m b e r o f o b s e r v a t i o n s}$

Let the last observation i.e the next number be X.

Therefore, new Total sum = 45 + X
new Total number of observations = 10

$\Rightarrow$ $5 = \frac{45 + X}{10}$

$\Rightarrow$ $50 = 45 + X$
$\Rightarrow$ $X = 5$

Therefore, the next number should be 5.

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A die is cast 9 times and the sum of all the observations (the observation being the number on the top face of the die) obtained till that point is 45. What should the next number be so that the average is 5?

The correct option is B 5We know, Average=Sum of all observationsTotal number of observations Let the last observation i.e the next number be X. Therefore, new Total sum = 45 + X new Total number of observations = 10 ⇒ 5=45+X10 ⇒ 50=45+X ⇒ X=5 Therefore, the next number should be 5.