The average of twelve numbers is 46. The average of the first four numbers is 43 and that of the last five numbers is 49.4. The 5th and the 6th numbers are respectively 4 and 6 more than the 7th number. What is the average of the 5th and 7th numbers?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 43.
Let the 7th number be x.
Sum of twelve numbers = 46 × 12 = 552
⇒ 552 = (43 × 4) + x + x + 4 + x + 6 + (49.4 × 5)
⇒ 3x = 552 – 429 = 123
⇒ x = 41
So, average of 5th and 7th number = = = 43