Average

 Average ( SET 3 : Q11-Q15 )

11.The average age of 6 students is 11 years. If two more students of ages 14 and 16 years join. What will their now average age ?
1
11
2
12
Correct Answer
3
13
4
14


Solution: 2

Given:

Aerage age of 6 students = 11 yrs

Formula used:

Average of n numbers = sum of total numbers/n

Calculation:

Total age before new students were added = 11 ×  6 = 66

Total age after new students were added = 66 + 14 + 16 = 96

Let their current average age be x

Then, according to the question:

⇒ x = 96/8

⇒ x = 12

∴ Their new average age = 12 years


12. The average weight of 30 girls is 40kg, another 40 girls is 30kg and another 20 girls is 20kg. Find the average weight of all the girls.
 28
2

Incorrect
3
30
4

Correct Answer



Solution: 4

The average weight of 30 girls is 40 kg

⇒The sum of weights of 30 girls = 40 × 30 = 1200 kg

The average weight of another 40 girls is 30 kg

⇒The sum of weights of 40 girls = 30 × 40 = 1200 kg

The average weight of another 20 girls is 20 kg

⇒ The sum of weights of 20 girls = 20 × 20 = 400 kg

Sum of weights of all the girls = 1200 + 1200 + 400 = 2800 kg

Total numbers of girls = 30 + 40 + 20 = 90

Average weight of all the girls = 2800/90 

∴The average weight of all the girls = 

13. The mean temperature from Monday to Wednesday was 40°C and on Tuesday was 36°C. The average of Tuesday to Thursday was 44°C. If the temperature of Thursday was 5/4th that of Monday, the temperature of Thursdays was
1
60.5°C
Incorrect
2
64°C
3
65°C
4
60°C
Correct Answer

Solution: 4

Let the temp. on Monday be M, Wednesday be W, and Thursday be Th. We have,

(M + 36 + W)/3 = 40

⇒ M + W = 120 – 36 = 84°C

⇒ W = 84 – M

Also, given

(36 + W + Th)/3 = 44

⇒ W + Th = 132 – 36 = 96°C

It is given that Th = 5M/4

⇒ W + 5M/4 = 96

⇒ W = 96 – 5M/4

84 – M = 96 – 5M/4

⇒ M/4 = 12

⇒ M = 48°C

⇒ Th = 5 × 48/4 = 60°C

14. The average age of a 15-member cricket squad is 19 years, if the coach’s age is included, the average increase to 22 years. What is the coach’s age?
1
67 years
Correct Answer
2
52 years
3
37 years
4
44 years

Solution: 1

Given, Average age of 15 members = 19

⇒ Sum of ages of 15 members = 15 × 19 = 285

Given, if the coach’s age is also included, we have average as 22 years.

⇒ (285 + Age of coach)/16 = 22

⇒ 285 + Age of coach = 16 × 22 = 352

⇒ Age of coach = 352 – 285 = 67 years

15. A tabulator while calculating the average marks of 100 students of an examination, by mistake enters a student’s marks as 68, instead of 86 and obtained the average as 58; the actual average is
1
58.18
Correct Answer
2
57.82
Incorrect
3
58.81
4
57.28

Solution: 1

Let the sum of the marks of the remaining 99 students be N.

⇒ N = 5800 – 68 = 5732

Hence, calculating the original average, we have


 SET 01 : Q1 - Q5

 SET 02 : Q6 - Q10

 SET 03 : Q11 - Q15

 SET 04 : Q16 - Q20

 SET 05 : Q21 - Q25

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