Question

The average of the first and the second of three numbers is 15 more than the average of the second and the third of these numbers. What is the difference between the first and the third of these three numbers?
1) 45
2) 15
3) 30
4) 60

Answer 1

Answer :
             Let first number = a
                  Second Number = b
                 Third Number =c
According to question,
       (a+b)/2 =(b+c)/2+15
    Multiply by 2 on b/s , we get
       a+b = b+c+2*15
       a+b = b+c + 30
      or a+b -b -c =30
     or a-c =30

Hence option (3) is answer !!!
 
Therefore , difference between firsxt number and third Number is 30.

Hope this helps you.
Thank You.
Tawseef