Question
In a class of 30 students, the average age each student
of the class is 21 years. 4 more students join the class such that the average age of the class decreases by 12 months. Find the average age of the 4 students who joined the class.Solution
Initial sum of ages of the students in the class = 21 × 30 = 630 years
New average age of the class = 21 - 1 = 20 years
New sum of ages of the students in the class = 20 × 34 = 680 years
Sum of ages of the new students = 680 - 630 = 50 years
Required average = 50 ÷ 4 = 12.5 years
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