Directions: Study the following questions carefully and answer the questions given below.
1
Vibhor obtained 66, 74, 55, 92, 79  (out of 100) in English, Maths, Physics, Chemistry and Biology. what's his average marks ?
» Explain it
C
So, let's make equation from the given information :

Average  =    ( 66 + 74 + 55 + 92 + 79 )  =   366
5 5

 Average  = 73.2% .
2
In Ashish’s  opinion, his weight is greater than 55 kg but less than 62 kg. His father does not agree with Ashish and he thinks that Ashish’s weight is greater than 50 kg but less than 60 kg. His sister’s view is that his weight can't be greater than 58 kg. If all of them are correct in their estimation, what is the average of different probable weights of Ashish ?
» Explain it
A
Let Ashish weight X kg.
 
According to Ashish , 55 < X < 62
 
According to Ashish's father,  50 < X < 60
 
According to Ashish's sister,  X < 58
 
The values satisfying all the above conditions are 56 & 57.
 
Therefore,  Required average =  ( 56 + 57 )   =   ( 113 )
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So, the Ashish's weight is  56.5 kg.  

3
The average of 15 numbers is zero. Of them, at the most, how many may be greater than zero?
» Explain it
A
Average of 15 numbers = 0.

Sum of 15 numbers = (0 × 15) = 0.
 
 
It is quite possible that 14 of these numbers may be positive and if their sum is a, then 15th number is (–a).
4
Find the average of all the numbers between 8 and 55 which are divisible by 7.
» Explain it
B
Multiples of 7 between 8 and 55 will be;

14, 21, 28, 35, 42, 49

Average =   ( First term + Last term )  =  14 + 49
2 2

  31.5.
5
The average of first five multiples of 5 is:
» Explain it
C
Multiple of 5 are: 5, 10, 15, 20, 25. so,

Average =   First term + Last term  =  (5 + 25)  = 15.
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