WAEC Mathematics

The mean of 1, 3, 5, 7 and x is 4. Find the value of x

Correct answer: B

Since the average of the numbers is 4, $(1 + 3 + 5 + 7 + x)÷5=4$ . After simplifying, you get

(16 + x)÷5=4 \\ \\ 16 + x = 20 \\ x=4