Average
- If the average of the ages of Rakesh and Mohan is 15, average of the ages of Mohan and Ramesh is 12 and the average of the ages of Rakesh and Rameh is 13, then the age of Mohan, is ?
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Let ages of Rakesh, Mohan and Ramesh be R, M and r, respectively .
Then, R + M = 15 x 2 = 30.......(i)
M + r = 12 x 2 = 24 ........(ii)
r + R = 13 x 2 = 26 ..... (iii)Correct Option: C
Let ages of Rakesh, Mohan and Ramesh be R, M and r, respectively .
Then, R + M = 15 x 2 = 30.......(i)
M + r = 12 x 2 = 24 ........(ii)
r + R = 13 x 2 = 26 ..... (iii)
Adding Eqs. (i), (ii) and (iii), we get
2(R + M + r) = 30 + 24 + 26 = 80
⇒ R + M + r = 40
Subtracting Eq. (iii) from Eq. (iv), we get
M = 40 - 26 = 14
- The average age of 5 sisters is 20 yr. If the age of the youngest sister be 4yr. What was the average age of the group of sister at the birth of the yongest sisiter ?
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Total age of 5 sister = 20 x 5 = 100 yr.
4 yr ago, total sum of ages
= 100 - ( 5 x 4) = 100 - 20 = 80 yr
But at that time (4 yr ago), there were 4 sister in the group.Correct Option: D
Total age of 5 sister = 20 x 5 = 100 yr.
4 yr ago, total sum of ages
= 100 - ( 5 x 4) = 100 - 20 = 80 yr
But at that time (4 yr ago), there were 4 sister in the group.
∴ Average age at that time(4 yr ago) = 80/4 = 20 yr.
- The average age of a committee of eight members is 40 years. A member aged 55 years retired and his place was taken by another member aged 39 years. Find the average age of the present committee.
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The average age of eight members = 40 years
Sum of age of 8 members = 8 × 40 = 320 years
After a person of age 55 years retires,
Sum of ages of 7 persons = 320 – 55 = 265 years
Sum of ages of 8 persons when a man of age 39 years joins it = 265 + 39 = 304 yearsCorrect Option: A
The average age of eight members = 40 years
Sum of age of 8 members = 8 × 40 = 320 years
After a person of age 55 years retires,
Sum of ages of 7 persons = 320 – 55 = 265 years
Sum of ages of 8 persons when a man of age 39 years joins it = 265 + 39 = 304 years
∴ Required average = 304 ÷ 8 = 38 years
- The average of 8 numbers is 21. If each of the numbers is multiplied by 8, find the average of new set of numbers.
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Given that , The average of 8 numbers = 21
Sum of eight numbers = 8 × 21 = 168
Now, each of the numbers is multiplied by 8.
∴ Sum of new eight numbers = 168 × 8 = 1344Correct Option: B
Given that , The average of 8 numbers = 21
Sum of eight numbers = 8 × 21 = 168
Now, each of the numbers is multiplied by 8.
∴ Sum of new eight numbers = 168 × 8 = 1344
∴ Average of new set of numbers = 1344 ÷ 8 = 168
- Out of four numbers, the average of first three is 15 and that of last three is 16. If the last number is 19, find the first number.
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Here , The last number = 19
The average of first three = 15
Sum of all four numbers = 3 × 15 + 19 = 64
The average of last three = 16
Sum of last three numbers = 3 × 16 = 48Correct Option: C
Here , The last number = 19
The average of first three = 15
Sum of all four numbers = 3 × 15 + 19 = 64
The average of last three = 16
Sum of last three numbers = 3 × 16 = 48
So, first number = 64 – 48 = 16
