Average problems
- 1. The average of runs of a cricket player of 10 innings was 32. How many runs must he make in his next innings so as to increase his average of runs by 4 ?
Options- A. 76
- B. 79
- C. 85
- D. 87 Discuss
Correct Answer: 76
Explanation:
Average = total runs / no.of innings = 32
So, total = Average x no.of innings = 32 x 10 = 320.
Now increase in avg = 4runs. So, new avg = 32+4 = 36runs
Total runs = new avg x new no. of innings = 36 x 11 = 396
Runs made in the 11th inning = 396 - 320 = 76
- 2. The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero ?
Options- A. 0
- B. -1
- C. 1
- D. none of these Discuss
Correct Answer: 0
Explanation:
Average of 20 numbers = 0.
Sum of 20 numbers = (0 * 20) = 0.
It is quite possible that 19 of these numbers may be positive and if their sum is a, then 20th number is (- a).
- 3. A grocer has a sale of Rs 6435, Rs. 6927, Rs. 6855, Rs. 7230 and Rs. 6562 for 5 consecutive months. How much sale must he have in the sixth month so that he gets an average sale of Rs, 6500 ?
Options- A. 4991
- B. 5467
- C. 5987
- D. 6453 Discuss
Correct Answer: 4991
Explanation:
Total sale for 5 months = Rs. (6435 + 6927 + 6855 + 7230 + 6562) = Rs. 34009.
Required sale = Rs.[(6500 x 6) - 34009]
= Rs. (39000 - 34009)
= Rs. 4991.
- 4. The average weight of 8 persons increases by 2.5 kg when a new person comes in place of one of them weighing 65 kg. What might be the weight of the new person ?
Options- A. 70 kg
- B. 75 kg
- C. 80 kg
- D. 85 kg Discuss
Correct Answer: 85 kg
Explanation:
Total weight increased = (8 x 2.5) kg = 20 kg.
Weight of new person = (65 + 20) kg = 85 kg.
- 5. The average weight of a class of 24 students is 35 kg. If the weight of the teacher be included, the average rises by 400 g. The weight of the teacher is :
Options- A. 45 kg
- B. 46 kg
- C. 47 kg
- D. 48 kg Discuss
Correct Answer: 45 kg
Explanation:
Weight of the teacher = (35.4 x 25 - 35 x 24) kg = 45 kg.
- 6. The mean temperature of Monday to Wednesday was 37 degree celsius and of Tuesday to Thursday was 34 degree celsius . If the temperature on Thursday was (4/5) th that of Monday, the temperature on Thursday was?
Options- A. 38 degree celsius
- B. 36 degree celsius
- C. 40 degree celsius
- D. 39 degree celsius Discuss
Correct Answer: 36 degree celsius
Explanation:
Let, temperature of Monday = a Temperature of Tuesday = b Temperature of Wednesday = c Temperature of Thursday = 4a/5 Sum of temperatures of Monday to Wednesday = 3×37 = 111 => a+b+c=111------(1) Sum of temperatures of Tuesday to Thursday = 3×34 = 102 b+c+(4a/5) = 102 ------(2) (1)-(2)=> a−(4a/5)=111−102 a/5=9 a=45 Temperature on Thursday = 4a/5 =4×45/5 =36
- 7. A pupil's marks were wrongly entered as 83 instead of 63. Due to that the average marks for the class got increased by half. The number of pupils in the class is :
Options- A. 45
- B. 40
- C. 39
- D. 37 Discuss
Correct Answer: 40
Explanation:
Let there be x pupils in the class.
Total increase in marks = (x * 1/2) = x/2.
x/2 = (83 - 63) => x/2 = 20 => x = 40.
- 8. The mean of 50 observations was 36. It was found later that an observation 48 was wrongly taken as 23. The corrected new mean is :
Options- A. 35
- B. 36.5
- C. 40
- D. 42 Discuss
Correct Answer: 36.5
Explanation:
Correct Sum = (36 * 50 + 48 - 23) = 1825.
Correct mean = = 1825/50 = 36.5
- 9. Of the four numbers, whose average is 60, the first is one-fourth of the sum of the last three. The first number is :
Options- A. 17
- B. 29
- C. 36
- D. 48 Discuss
Correct Answer: 48
Explanation:
Let the first number be x,
Then, sum of the four numbers = x + 4x = 5x.
so, 5x/4 = 60 or x = (60 * 4) / 5 = 48.
- 10. Out of 9 persons, 8 persons spent Rs. 30 each for their meals. The ninth one spent Rs. 20 more than the average expenditure of all the nine. The total money spent by all of them was :
Options- A. Rs. 292.50
- B. Rs. 297.50
- C. Rs. 298
- D. Rs. 298.50 Discuss
Correct Answer: Rs. 292.50
Explanation:
Let the average expenditure be Rs. x Then,
9x=[(8*30)+(x+20)]<=>9x =x+260 <=> x =32.50
Total money spent = 9x = Rs. (9 x 32.5O) = Rs 292. 50
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