Average, General Mathematics

Question: In a cricket eleven ,the average of eleven players is `28` years.Out of these, the average ages of three groups of three players each are `25` years, `28`years and `30`years respectively.If in these groups, the captain and the youngest player are not included, and the captain and the youngest player, what is the age of the captain ?
A
`33 years`

B
`34 years`

C
`35 years`

D
`36 years`

Note: Let the age of youngest player be x. Then, age of the captain `= (x + 11)` `:. 3 xx 25 + 3 xx 28 + 3 xx 30 + x + x + 11` `= 11 xx 28` `⇒ 75 + 84 + 90 + 2x + 11` `= 308 ⇒ 2x = 48` `⇒ x = 24`. :. Age of the captain `= (x + 11)` `= 35 years`
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Question: After replacing an old member by anew member, it was found that the average age of five members of a club is the same as it was `3` years ago. What is the difference between the ages of the replaced and the new mwmber ?
A
`15 yrs`

B
`8 yrs`

C
`4 yrs`

D
`2 yrs`

Note: Age decreased `= (5 xx 3) years` `= 15 years` So, the required difference `= 15 years`
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Question: The average age of a class is `15.8 years`The average age of the boys in the class is `16.4 years` while that of the girls is `15.4 years.What is the ratio of boys to girls in the class
A
`1 : 2`

B
`3 : 4`

C
`3 : 5`

D
None of these

Note: Let the ratio be` k : 1`.Then `k xx 16.4 + 1 xx 15.4` `= (k + 1) xx 15.8` `or (16.4 - 15.8) k` `= (15.8 - 15.4)` `or k = 0.4/0.6` `= 2/3` :. Required ratio `= 2/3 : 1` `= 2 : 3`.
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Question: The average age of `3` children in a family is `20‰` of the average age of the father and the eldest child. The total age of the mother and the youngest child is `39` years. If the father,s age is `26` years, what is the age of second child ?
A
`15 yrs`

B
`18 yrs`

C
`20 yrs`

D
Can not be determined

Note: Since the total or average age of all the famial members is not given, the given data is inadequate .So the age of second child cannot be determind.
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Question: After replacing an old member by anew member, it was found that the average age of five members of a club is the same as it was `3` years ago. What is the difference between the ages of the replaced and the new mwmber ?

Question: The average age of a class is `15.8 years`The average age of the boys in the class is `16.4 years` while that of the girls is `15.4 years.What is the ratio of boys to girls in the class

Question: The average age of `3` children in a family is `20‰` of the average age of the father and the eldest child. The total age of the mother and the youngest child is `39` years. If the father,s age is `26` years, what is the age of second child ?