If 24 students took a test and the average was 50, what was the sum of the scores?
A useful re-write of the average formula:
sum of items = (average) x (number of items)
sum = 24 x 50
Use the doubling and halving trick:
half of 24 = 12
double of 50 = 100
sum = 24 x 50 = 12 x 100 = 1200