Question

Solution the average of the first four of five numbers is 40 and that of the last four numbers is 60. the difference of the last and the first number is:

Answer 1

difference between 1st and last will be 80

Answer 2

Let numbers are ( a, b, c, d, e )

a = first number
e = last number




Average of first 4 = ( a + b + c + d ) / 4

=> 40 = ( a + b + c + d ) / 4

=> 160 = a + b + c + d -----1equation





Average of last 4 numbes = ( b + c + d + e ) / 4

60 = ( b + c + d + e ) / 4

=> 240 = b + c + d + e ---2equation




Now, subtract 1equation from. 2quation



240 = b + c + d + e
160 = a + b + c + d
-___(-)_(-)_(-)_(-) ___
80 = a - e
_______________




$.$

=> 80 = last number - fist number
=> 80 = difference of last and first term