Question

the average of the five number was 6.8. If the first four numbers were 4.3, 5.2, 7, and 6.8, What was the fifth number?

Answer 1

Let x be the fifth number
$\frac{4.3 + 5.2 + 7 + 6.8 + x}{5} = 6.8$
⇔ $\frac{23.3 + x}{5} = 6.8$
⇔ 23.3 + x = 34
⇔ x = 10.7