Question

there are four unknown numbers.The mean of first two number is four and the mean of the first three is 9.The mean of all four numbers is 15,if one of the four number is 2 find the other number

Answer 1

Always assume the numbers first and write the problem in mathematical form. This will really simplify it. Hope this helps

Answer 2

Answer:

The required numbers are 2,6,19 and 33.

Step-by-step explanation:

Given : There are four unknown numbers.The mean of first two number is four and the mean of the first three is 9.The mean of all four numbers is 15,if one of the four number is 2.

To find : The other number ?

Solution :

Let the numbers be p,q,r and s.

According to question,

The mean of first two number is four and the mean of the first three is 9.The mean of all four numbers is 15.

i.e.

$\frac{p+q}{2}=4$ .....(1)

$\frac{p+q+r}{3}=9$ ......(2)

$\frac{p+q+r+s}{4}=15$  ......(3)

If one of the four number is 2 so we let p=2,

Substitute in equation (1),(2) and (3).  

In equation (1),

$\frac{2+q}{2}=4$

$2+q=8$

$q=6$

In equation (2),

$\frac{2+6+r}{3}=9$

$8+r=27$

$r=19$

In equation (3),

$\frac{2+6+19+s}{4}=15$

$27+s=60$

$s=33$

Therefore, The required numbers are 2,6,19 and 33.