Average
- In a school with 600 students, the average age of the boys is 12 years and that of the girls is 11 years. If the average age of the school is 11 years and 9 months, then the number of girls in the school is
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Let the number of girls = y
And Number of boys = 600 – y
According to question ,∴ (600 – y ) × 12 + 11y = 11 3 × 600 = 47 × 600 4 4
Correct Option: B
Let the number of girls = y
And Number of boys = 600 – y
According to question ,∴ (600 – y ) × 12 + 11y = 11 3 × 600 = 47 × 600 4 4
⇒ 7200 – 12y + 11y = 7050
⇒ y = 7200 – 7050 = 150
Hence , the number of girls is 150.
- In a school, the average age of students is 6 years, and the average age of 12 teachers is 40 years. If the average age of the combined group of all the teachers and students is 7 years, then the number of students is :
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Let the number of students be n. Then,
According to question ,7 = n × 6 + 12 × 40 n + 12
Correct Option: A
Let the number of students be n. Then,
According to question ,7 = n × 6 + 12 × 40 n + 12
⇒ 7n + 84 = 6n + 480
⇒ n = 480 – 84 = 396
- The average age of a husband and wife, who were married 4 years ago, was 25 years at the time of their marriage. The average age of the family consisting of husband, wife and a child, born during the interval is 20 years today. The age of the child is
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Here , The average age of a husband and wife, who were married 4 years ago = 25 years
Sum of the present age of husband and wife
= 2 × 25 + 2 × 4 = 58 years
The average present age of husband, wife and a child = 20 years
Sum of the present age of husband, wife and child = 3 × 20 = 60 yearsCorrect Option: B
Here , The average age of a husband and wife, who were married 4 years ago = 25 years
Sum of the present age of husband and wife
= 2 × 25 + 2 × 4 = 58 years
The average present age of husband, wife and a child = 20 years
Sum of the present age of husband, wife and child = 3 × 20 = 60 years
∴ Child’s present age = 60 – 58 = 2 years
- The average age of a husband and a wife was 27 years when they married 4 years ago. The average age of the husband, the wife and a new-born child is 21 years now. The present age of the child is
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Given that , 4 years ago , The average age of a husband and a wife = 27 years
Sum of the present age of husband and wife = 2 × 27 + 8 = 62 years
The average age of the husband, the wife and a new-born child = 21 years
Sum of the present age of husband, wife and child = 21 × 3 = 63 yearsCorrect Option: D
Given that , 4 years ago , The average age of a husband and a wife = 27 years
Sum of the present age of husband and wife = 2 × 27 + 8 = 62 years
The average age of the husband, the wife and a new-born child = 21 years
Sum of the present age of husband, wife and child = 21 × 3 = 63 years
∴ present age of the child = 63 – 62 = 1 year
- The average age of eleven cricket players is 20 years. If the age of the coach is also included, the average age increases by 10%. The age of the coach is
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Here , The average age of eleven cricket players = 20 years
Total age of 11 players = 11 × 20 = 220 years
If the age of the coach is also included, the average age increases by 10%
i.e. Total increase average = 20 of 10% = 2
New average of 11 players and the coach = 20 + 2 = 22 years
Total age of 11 players and the coach = 12 × 22 = 264 yearsCorrect Option: B
Here , The average age of eleven cricket players = 20 years
Total age of 11 players = 11 × 20 = 220 years
If the age of the coach is also included, the average age increases by 10%
i.e. Total increase average = 20 of 10% = 2
New average of 11 players and the coach = 20 + 2 = 22 years
Total age of 11 players and the coach = 12 × 22 = 264 years
∴ Age of the coach = (264 – 220) years = 44 years
