The average of 6 numbers is 30. If the average of the first four is 25 and that of the last three is 35, the fourth number is?
- 15
- 30
- 25
- 20
Explanation
Avg of 6 numbers = 30Sum of 6 numbers = 6 x 30 = 180
Avg of first 4 numbers = 25
Sum of first 4 numbers = 4 x 25 = 100
Avg of last 3 numbers = 35
Sum of last 3 numbers = 3 x 35 = 105
Now, let's find the 4th number:
Sum of first 3 numbers = Sum of first 4 numbers - 4th number
= 100 - 4th number
Sum of first 3 numbers = Sum of all 6 numbers - Sum of last 3 numbers
= 180 - 105
= 75
So, 75 = 100 - 4th number
4th number = 100 - 75
= 25
Last verified on 24-10-2026
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