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Q.

The average of 50 numbers is 30. If two numbers, 35 and 40 are discarded, then the average of the remaining numbers is nearly:

 A.

28.32

 B.

29.68

 C.

28.78

 D.

29.27

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Solution:
Option(B) is correct

Total sum of 48 numbers $= (50 \times 30) - (35 + 40) $

$= 1500 - 75$

$= 1425$

Average $=\left(\dfrac{1425}{48}\right)$

29.68

Edit: For an alternative appraoch to solve the question, check comment by Sravan Reddy.


(5) Comment(s)


Sravan Reddy
 ()

Some quick mind thinking (May be difficult to follow initially but would work great with averages if mastered)

Always remove the average values first. So assuming just two 30's are discarded, the average still is 30 with 48 numbers. But additionally 15 got removed $(35+45-30-30=15)$.

So, $\dfrac{15}{48}$ is the desired value that needs to be subtracted from 30 to get the answer


Anil
 ()

what is this $\dfrac??

Ali
 ()

Please re correct (35+40-30-30=15)


Parul
 ()

cant dis be done with unitary method??

which says

50 numbers have an avrage of 30

so 48 no will hv average of \dfrac{30}{50}\times 48$

and if this is correct.. I am getting answer as 28.8



Anita
 ()

initially, the total sum of the numbers:

$=50 \times 30=1500$

after discarding the two numbers $35,40$ the sum becomes:

$1500-35-40=1425$

Now the total number of terms left is:

$50-2=48$.

As we know:

$$ \textbf{Average} =\dfrac{\textbf{Total Sum}}{\textbf{Total no of Terms}}$$

Substituting the values in the above formula,

Average $=\dfrac{1425}{48}$

$=\textbf{29.68}$