Question
The average age of 18 girls is 36 years. If the age of
two more girls is added the average decreases by half a year. What is the sum of the age of new girls?Solution
Total age of 18 girls = 18 × 36 = 648 years  If the age of two more girls is added the average decreases by half a year,  ∴ Total age of 20 girls = 35.5 × 20 = 710 Now, sum of the age of new girls = 710 – 648 = 62 years
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