1.

The average of boys is 18 years in a class of 30 if 10 more boys jion the class the average of the whole class gets increasedby a years what is the average age of newcomers

Answer»

ANSWER:

let sum of age of 30 students of class = x

then AVERAGE of these 30 students = x / 30

also average given = 18

so x/30 = 18

solving for x gives = 18 * 30

x=540

let sum of age of NEW 10 students = y

average of these 40 students = (x+y) / 40

also average of these 40 students = 19

putting value of x = (540 + y) / 40

solving for y = (540 + y) / 40 = 19

540+y = 40 * 19

540 + y = 760

y = 220

then average of these 10 students = ( sum of their age) / 10

average = y/10

average = 22


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