Average
- The average age of 30 boys in a class is 10 years. If the age of their teacher is also included, the average increases by one year. The teacher’s age in years is
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Given that , The average age of 30 boys = 10 years
On including teacher , total increase = 31 × 1 = 31 years
Teacher’s age = The average age of 30 boys + total increaseCorrect Option: D
Given that , The average age of 30 boys = 10 years
On including teacher , total increase = 31 × 1 = 31 years
Teacher’s age = The average age of 30 boys + total increase
∴ Teacher’s age = (10 + 31) years = 41 years
- The average age of 36 students in a group is 14 years. When the teacher’s age is included in it, the average increases by one. The teacher’s age in years is
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Here , The average age of 36 students = 14 years.
Total age of 36 students = 36 × 14
Let teacher’s age be y years.
According to the question,
36 × 14 + y = 37 × 15
⇒ 504 + y = 555Correct Option: B
Here , The average age of 36 students = 14 years.
Total age of 36 students = 36 × 14
Let teacher’s age be y years.
According to the question,
36 × 14 + y = 37 × 15
⇒ 504 + y = 555
⇒ y = 555 – 504 = 51 years
- The average age of eight teachers in a school is 40 years. A teacher among them died at the age of 55 years whereas another teacher whose age was 39 years joins them. The average age of the teachers in the school now is (in years)
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The average age of eight teachers = 40 years
According to question ,
Difference between ages = 39 – 55 = – 16 years∴ Required average = 40 – 16 9 Correct Option: C
The average age of eight teachers = 40 years
According to question ,
Difference between ages = 39 – 55 = – 16 years∴ Required average = 40 – 16 = 38 year 9
- The sum of the ages of mother and her daughter is 60 years. 12 years ago the mother was eight times as old as her daughter. How old is the daughter at present?
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Let Daughter’s present age = y years
∴ Mother’s present age = (60 – y) years
According to the question,
12 years ago, (60 – y – 12) = 8 (y – 12)
⇒ 48 – y = 8y – 96
⇒ 8y + y = 96 + 48Correct Option: C
Let Daughter’s present age = y years
∴ Mother’s present age = (60 – y) years
According to the question,
12 years ago, (60 – y – 12) = 8 (y – 12)
⇒ 48 – y = 8y – 96
⇒ 8y + y = 96 + 48
⇒ 9y = 144
⇒ y = 144 ÷ 9 = 16 years
- The average age of 10 children is 9 years 9 months. The average age of 9 children is 8 years 11 months. What is the age of the tenth child ?
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Given that , The average age of 10 children = 9 years 9 months
Total age of 10 children = ( 9 years 9 months ) × 10
The average age of 9 children = 8 years 11 months
Total age of 9 children = ( 8 years 11 months ) × 9
∴ Age of tenth child = (9 years 9 months) × 10 – (8 years 11 months) × 9Correct Option: A
Given that , The average age of 10 children = 9 years 9 months
Total age of 10 children = ( 9 years 9 months ) × 10
The average age of 9 children = 8 years 11 months
Total age of 9 children = ( 8 years 11 months ) × 9
∴ Age of tenth child = (9 years 9 months) × 10 – (8 years 11 months) × 9
Age of tenth child = 97 years 6 months – 80 years 3 months = 17 years 3 months
