Question : The average of twelve numbers is 39. The average of the last five numbers is 35, and that of the first four numbers is 40. The fifth number is 6 less than the sixth number and 5 more than the seventh number. The average of the fifth and sixth numbers is:
Option 1: 47
Option 2: 39
Option 3: 44
Option 4: 50
Correct Answer: 47
Solution :
The average of twelve numbers is 39.
Sum of twelve numbers = 39 × 12 = 468
The average of the last five numbers = 35
The sum of last five numbers = 35 × 5 = 175
Average of the first four numbers = 40
The sum of the first four numbers = 40 × 4 = 160
Let
Sixth number =
Seventh number =
So,
⇒
⇒
Average of fifth and sixth number =
Hence, the correct answer is 47.
