The average of 18 numbers is 42. The average of the last 10 numbers 40 and that of the first five numbers is 44, then the seventh number is 6 less than the sixth and 7 less than the 8th number. Then the average of 6th and 8th number is?
Answer & explanation
Correct answer: option 1
⇒ 10 × (-42 + 40) + 5 × (44 - 42)
⇒ 10 × -2 + 10 = -10
Deviation is = -10
Now, sum of three numbers = 42 × 3 + 10 = 136
6th 7th 8th
x x-6 x+1
3x - 5 = 136
x = 47
So, 6th = 47
8th = 48
Average = \(\frac{47 + 48}{2}\) = 47.5