# Word Problem 9

Problem 9: The average age of 600 students in a class is 10.75 years, by enrollment of 40 new students the average age is lowered to 10.437 years. Find the average age of the new students.

a) 6.0                 b) 5.75                     c) 5.15                d) 5.50

(math test for jobs)

 (adsbygoogle = window.adsbygoogle || []).push({}); 

Solution:

Note: We will solve this problem in easy way- though it can be solved in one or two steps in no time !

Suppose there are 600 students with ages,

x1,x2,x3 ………………..x600

Then their average age will be obtained by summing up their ages , divided by number of students i-e 600;

So,

But average age of 600 students is given as 10.75

or

Now suppose new 40 students  have ages y1, y2, y3…………….y40

So now total students are 640.

And average age of 640 students again ca be calculated by summing up their ages and dividing the sum number of students i-e 640

If seen by supposition  , total age of 640 students is

Put value of         x1+x2+x3+……….x600     from eq (1);

But it is given that after joining of new 40 student the average age becomes  10.437

Divide both sides by 40

But,