Average
- After replacing an old member by a new member, it was found that the average age of five members of a club is the same as it was 3 years ago. The difference between the ages of the replaced and the new members is
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According to question ,
Increase in ages of five members in 3 years = (3 × 5) years = 15 years
As average age remains same,Correct Option: D
According to question ,
Increase in ages of five members in 3 years = (3 × 5) years = 15 years
As average age remains same,
∴ Required difference = 15 years
- Three years ago, the average age of a family of 5 members was 17 years. A baby having been born the average age of the family is the same today. The present age of the baby (in years) is
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Here , Three years ago, the average age of 5 members = 17 years
Three years ago, Total age of the family = 17 × 5 = 85 years
Total age of 5 member family today = 85 + 15 = 100 years
Born on baby , the average age of 6 members = 17 years
Total age of the family with child today = 17 × 6 = 102 yearsCorrect Option: A
Here , Three years ago, the average age of 5 members = 17 years
Three years ago, Total age of the family = 17 × 5 = 85 years
Total age of 5 member family today = 85 + 15 = 100 years
Born on baby , the average age of 6 members = 17 years
Total age of the family with child today = 17 × 6 = 102 years
Age of baby = 102 – 100 = 2 years
- Three years ago, the average age of a family of 5 members was 17 years. A baby having been born, the average age of the family is the same today. The present age of the baby is:
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Here , Three years ago, the average age of 5 members = 17 years.
Total age of the family 3 years ago = 5 × 17 = 85 years
Total present age of the family = 85 + 15 = 100 years
Let the child’s present age be y years.
According to the question,
100 + y = 17 × 6 = 102Correct Option: A
Here , Three years ago, the average age of 5 members = 17 years.
Total age of the family 3 years ago = 5 × 17 = 85 years
Total present age of the family = 85 + 15 = 100 years
Let the child’s present age be y years.
According to the question,
100 + y = 17 × 6 = 102
⇒ y = 102 – 100 = 2 years
Hence , the child’s present age is 2 years.
- Numbers of boys and girls are ‘x’ and ‘y’ respectively. Ages of a girl and a boy are ‘a’ years and ‘b’ years respectively. The average age (in years) of all boys and girls is
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According to question ,
Total age of boys = ap years
Total age of girls = bq yearsCorrect Option: C
According to question ,
Total age of boys = ap years
Total age of girls = bq years∴ Required average = ap + bq p + q
- A man had 7 children. When their average age was 12 years, a child aged 6 years died. The average age of remaining six children is
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Here , The average age of 7 children = 12
Total age of 7 children = 12 × 7
Age of died child = 6 years
Total age of remaining 6 children = 12 × 7 – 6 = 84 – 6
Total age of remaining 6 children = 78 yearsCorrect Option: A
Here , The average age of 7 children = 12
Total age of 7 children = 12 × 7
Age of died child = 6 years
Total age of remaining 6 children = 12 × 7 – 6 = 84 – 6
Total age of remaining 6 children = 78 years
∴ Their average age = 78 ÷ 6 = 13 years
