Question 38

The total of the ages of a class of 60 girls is 900 years. The average age of 20 of the girls is 12years and that of the other 20 girls is 16 years. What is the average age of the remaining girls ?

Solution

Sum of the ages of 60 girls = 900

Sum of the ages of first 20 girls = 12 * 20 = 240

Sum of the ages of other 20 girls = 16 * 20 = 320

Remaining girls = 60 - 20 - 20 = 20

Sum of the ages of remaining 20 girls = 900 - 240 - 320 = 340

=> Average age of the remaining 20 girls = $$\frac{340}{20} = 17$$ years

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