Question

The average of 6 numbers is 30. If the average of first four is 25 and that of last three is 35,find the fourth number.​

Answer 1

Answer:

If the average of 6 numbers is given as 30 and the average of the first four numbers is given as 25 and the average of the last three numbers is 35, then the fourth number is 25

Step-by-step explanation:

Let a, b, c, d, e, and f be the 6 numbers whose average is 30

Given

Average of 6 numbers = 30

That is

$\frac{a+b+c+d+e+f}{6} = 30\\\\a+b+c+d+e+f= 30*6 = 180$

Also given

Average of first 4 numbers = 25

That is

$\frac{a+b+c+d}{4} = 25\\ \\ a+b+c+d = 25*4 = 100$

That is e + f = 180- 100

= 80

Also given that the average of the last three numbers is 35

That is

$\frac{d+e+f}{3} = 35\\ \\ d+e+f = 35*3 = 105$

e+f =80

So,

$d+ 80 = 105\\ d = 105-80\\ = 25$

The fourth number is d

Hence the fourth number is 25