Average problems
- 1. A class is divided into two sections A and B. Passing average of 20 students of section A is 80% and passing average of 30 students of sections B is 70%. What is the passing average of both the sections?
Options- A. 72%
- B. 74%
- C. 75%
- D. 77% Discuss
Correct Answer: 74%
Explanation:
Here n1 = 20, n2 = 30, a1 = 80%, a2 = 70%
? Total average = (n1a1 + n2a2) / (n1 + n2)
= (20 x 80 + 30 x 70) / (20 + 30)
= (1600 + 2100) / 50
= 74%
- 2. The average age of 4 member of family is 20 yr. If youngest member is 4 yr. old, What was the average age of family at the time of the birth of youngest member?
Options- A. 27 yr
- B. 231/3 yr
- C. 211/3 yr
- D. 22 yr Discuss
Correct Answer: 211/3 yr
Explanation:
Total age of all members of the family (at present) = 20 x 4 = 80
4yr ago, total age of all members = 80 - ( 4 x 4) = 80- 16 = 64 yr.
As 4 yr ago, there were only 3 members in the family
? Average age of the family at the time of the birth of the youngest member
= 64/3
= 211/3 yr
- 3. 3 yr ago, the average age of a family of 5 members was 17 yr. Even after the birth of a child, the aveage is same today. Find out the age of child.
Options- A. 1 yr
- B. 3 yr
- C. 21/2
- D. 2 yr Discuss
Correct Answer: 2 yr
Explanation:
3 yr ago, total age of 5 members of the family = 17 x 5 = 85 yr
Present age of all the members of the family = 85 + 3 x 5 = 100 yr
Let the age of the child = N yr
Present avrage age of family = (100 + N) / 6
[At present total number of members = 5 + 1 = 6]
17 = 100N / 6
? 102 = 100 + N
? N = 2 yr
- 4. A person bought some oranges worth ? 36 from each of the five markets at ? 1, ? 1.50, ? 1.80, ? 2 and ? 2.25 per orange, respectively. What is the average price of an orange?
Options- A. ? 1.91
- B. ? 2.00
- C. ? 1.58
- D. ? 1.80 Discuss
Correct Answer: ? 1.58
Explanation:
Number of oranges bought by the person
= 36/1 + 36/1.50 + 36/1.80 + 36/2 + 36/2.25
= 36 + 24 + 20 + 18 + 16
= 114
Total expenditure = 36 x 5 = ? 180
Thus, average price of each orange
= ? 180/114
= ? 1.58
- 5. Average of a, b and c is 11; average of c, d and e is 17; average of e and f is 22 and average of e and c is 17. Find out the average of a, b, c, d, e and f?
Options- A. 152/3
- B. 181/2
- C. 211/3
- D. 161/2 Discuss
Correct Answer: 152/3
Explanation:
According to the question,
a + b + c = 11 x 3 = 33 ......(i)
c + d + e = 17 x 3 = 51 ...........(ii)
e + f = 22 x 2 = 44 ........... (iii)
e + c = 17 x 2 = 34 ..........(iv)
From Eqs. (ii) and (iv), we get
34 + d = 51
or d = 17 ....(v)
Now, by adding Eqs. (i), (iii) and (v), we get
a + b + c + d + e + f = 33 + 44 + 17 = 94
? Average of a, b, c, d, e and f = 94/6
= 47 / 3
= 152/3
- 6. The average age of 54 girls in a class was calculated as 14 yr. It was later relized that the actual age of one of the girls in the class was 10.5 yr but it was calculated as 13 yr. What is the actual averge age (round off) of the the girls in the class? (Find the approximate answer.)
Options- A. 10.50 yr.
- B. 12.50 yr
- C. 12 yr
- D. 14 yr Discuss
Correct Answer: 14 yr
Explanation:
Total actual age of 54 girls = (54 x 14) - 13 + 10 .5
= 753.5 yr
? Require average age = 753.5/54
= 13.95 yr
= 14 yr(approx).
- 7. The average age of a man and his two twin sons born on the same day is 30 yr. The ratio of the ages of father and one son is 5 : 2, What is the father's age?
Options- A. 50 yr
- B. 30 yr
- C. 45 yr
- D. 20 yr Discuss
Correct Answer: 50 yr
Explanation:
According to the question,
Average age of man and his twin sons = 30
? Total age = 30 x 3 = 90 yr.
According to the question,
Ratio of father and one son = 5 : 2
? Ratio of father and both the sons = 5 : 2 : 2
(As sons are born on the same day.)
? 5k + 2k + 2k = 90 or 9k = 90
? k = 10
? Age of father = 5 x 10 = 50 yr.
- 8. The ratio of pens and pencil in a stationary shop is 3 : 2, respectively, The average number of pens and pencils is 180. What is the 30% of number of pencils in the shop?
Options- A. 150
- B. 144
- C. 245
- D. 115 Discuss
Correct Answer:
Explanation:
The average number of pens and pencils = 180
? Totol number of pens and pencils = 180 x 2 = 360
? Total number of pencils in the shop = 360 x (2/5) = 144
? 30% of 144 = (30/100) x 144 = 43.2 = 43
= 43 (approx)
- 9. 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?
Options- A. 16
- B. 13
- C. 14
- D. 12 Discuss
Correct Answer: 14
Explanation:
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
- 10. 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?
Options- A. 25 yr
- B. 15 yr
- C. 18 yr
- D. 20 yr Discuss
Correct Answer: 20 yr
Explanation:
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.
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