Question

6: the average of six numbers is 30.if the average of first four is 25 and that of last three is 35, the fourth number is?

Answer 1

6 nos average is 30 that means sum is 180 , first 4 is 25 so sum is 100 , last 3 is 35 so sum is 105 so 25 is the answer , as first 4 we have 100 total is 180 so 80 left for last 2 but 105 for last 3 is given so we subtract 80 from 105 we get 25 answer

Answer 2

The 4th number is 25.

Given:

Average of 6 numbers = 30, average of first four number = 25 and average of last three number = 35

To find:

The fourth number

Solution:

The Average of 6 numbers = 30.

∴ The Total Sum of 6 numbers$=30 \times 6=180$

The Average of first 4 numbers = 25.

∴ The Total Sum of first 4 numbers $=25 \times 4=100$

The Average of last 3 numbers = 35.

∴ The Total Sum of last 3 numbers $=35 \times 3=105$

Hence, the 4th number = (Total Sum of first 4 numbers + Total Sum of last 3 numbers) – Sum of all 6 numbers  

             = (100 +105) – 180

             = 205 – 180

             = 25