The average of the first four numbers is five times the fifth number. If the average of all five numbers is 84, then the fifth number is?
Answer & explanation
Correct answer: option 3
Let fifth number = x
Avg. of first 4 number = 5x
Sum of first 4 number = 5x × 4 = 20 x
Avg. = \(\frac{20x + x}{5}\) = 84
⇒ 21 x = 84 × 5
x = 20