JAMB - Mathematics (2002 - No. 39)
The mean of a set of six numbers is 60. If the mean of the first five is 50, find the sixth number in the set.
105
100
95
110
Explication
Let the sum of the first five numbers and the sixth number be x and t respectively.
\(\frac{x + t}{6} = 60 \implies x + t = 360\)
\(\frac{x}{5} = 50 \implies x = 250\)
\(\therefore t = 360 - 250 = 110\)