The average of the numbers a, b, c and d is 2d + 4. Also, the averages of the numbers a and b, b and c and d are 8, 5 and 4, respectively. If e = a + d + I, then what is the average of the numbers d and e?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 8
Average = Total of all observations/number of observation
(a+b+c+d)/4 = 2d + 4
a+b+c+d = 8d + 16
Similarly,
a + b = 16
b + c = 10
c + d = 8
8d + 16 = a + b + c + d
⇒ 8d + 16 = 16 + 8
⇒ 8d = 8
⇒ d = 1
Now for a
a + 10 + 1 = 24
⇒ a = 13
So
e = a + d + 1
⇒ e = 13 + 1 + 1
⇒ e = 15
Now,
(e+d)/2 = (15 + 1)/2 = 16/2
⇒ 8