Average problems
- 1. The average age of A,B,C,D and E is 40 years.The average age of A and B is 35 years and the average age of C and D is 42 years .The age of E is
Options- A. 46
- B. 48
- C. 32
- D. none of these Discuss
Correct Answer: 46
Explanation:
Age E = ( A + B + C + D + E ) - [ ( A + B ) + ( C + D ) ]
= ( 40 x 5 ) - [ ( 35 x 2 ) + ( 42 x 2 )]
=200 - ( 70 + 84)
= 200 - 154
= 46
- 2. Find the average of 308, 142, 160, 245 and 25.
Options- A. 176
- B. 178
- C. 175
- D. 174 Discuss
Correct Answer: 176
Explanation:
sum of observations
= 308 + 142 + 160 245 + 25 = 880
Average = Sum of all observations / Number of observations
=880 / 5
=176
- 3. The average age of a group of 10 friends is 15 yr. If one friend leaves the group, the average becomes 16 yr. Find the age of the friend who left the group.
Options- A. 5 yr
- B. 4 yr
- C. 6 yr
- D. None of these Discuss
Correct Answer: 6 yr
Explanation:
Age of friend left = Previous average of the age - Number of persons present x Increase in average age
= 15 - ( 10-1 ) x ( 16-15 )
= 15- 9 x 1
= 15 - 9 = 6yr
- 4. What is the average of first 79 natural numbers?
Options- A. 79
- B. 39
- C. 40
- D. 39.5 Discuss
Correct Answer: 40
Explanation:
Average of first n natural numbers = ( n + 1 ) / 2
= ( 79 + 1 ) / 2
= 40
- 5. The average of 8 number 21. if each of the number is multiplied by 8,the new set of number is?
Options- A. 8
- B. 21
- C. 29
- D. 168 Discuss
Correct Answer: 168
Explanation:
Average will increase by 8 times.
So average of new members = (21 x 8 ) = 168
- 6. The average of 50 number is 38 .if two numbers 45 and 55 are discarded , the average of the remaining number is?
Options- A. 36.5
- B. 37.0
- C. 37.5
- D. 37.52 Discuss
Correct Answer: 37.5
Explanation:
Sum of 50 member = (50 x 38 )
= 1900
Sum of 48 member = [1900- (45 + 55 ) ]
= 1800
? Required Average = 1800/48
= 225/6
= 37.5
- 7. The average score of a cricketer for 10 matches is 43.9 runs. If the average for the first six matches is 53 , the average for the last four matches is?
Options- A. 17.15
- B. 29.75
- C. 30.25
- D. 31 Discuss
Correct Answer: 30.25
Explanation:
Let the average for last 4 matches be y.
Sum of score for 10 matches = sum of score for first 6 matches + sum of score of last 4 matches.
So 53 x 6 + 4y = 10 x 43.9
? 4x= 439-318
?4x= 121
? x= 30.25
- 8. The average height of 30 girls out of a class of 40 is 160 cms and that of the remaining girls is 156 cms. the average height of the whole class is?
Options- A. 11.8
- B. 25
- C. 29.5
- D. 30 Discuss
Correct Answer: 30
Explanation:
Average height of the whole class = sum of height of 40 girls / 40
= (30 x 160 + 10 x 156) / 40
= 159 cms.
- 9. If a, b, c, d, e are five consecutive odd number , their average is?
Options- A. 5 (a + 4)
- B. abcd/5
- C. 5 (a + b + c + d + e)
- D. None of these Discuss
Correct Answer: None of these
Explanation:
Since a, b, c, d, e are 5 consecutive numbers so
b = a + 2.
c = a + 4.
d = a + 6.
e = a + 8.
Average = (a + b + c + d + e)/ 5
= [a + (a + 2 ) + (a +4 ) + (a+6 )+ (a+8)] / 5
= (5a+20) / 5
= a + 4
- 10. Out of three numbers, the first is twice the second and is half of the third. If the average of three number is 56, the three number in order are?
Options- A. 48, 96, 24
- B. 48, 24, 96
- C. 96, 24, 48
- D. 96, 48, 24 Discuss
Correct Answer: 48, 24, 96
Explanation:
Let second number = x
So, first number = 2x and third number= 4x
? ( x + 2x + 4x ) / 3 = 56
? 7x = 168
? x = 24
So the numbers are 48,24, 96,
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