model 5 find new average from error Section-Wise Topic Notes With Detailed Explanation And Example Questions
MOST IMPORTANT quantitative aptitude - 9 EXERCISES
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Basic Average Questions Practice Test, Shortcuts, Tricks, PDF »
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New Average Aptitude MCQ Average of Consecutive Numbers »
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Top 99+ Average Aptitude: Twice, One Third of Numbers MCQ »
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New +99 Average Aptitude MCQ Find nth Average of Numbers »
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99+ Average Aptitude Find New Average from Error MCQ Test »
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Top 99+ Aptitude MCQ Test on Average With Excluded Number »
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Top 99+ Aptitude Average on Ages & Weights MCQ Test Quiz »
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Top Aptitude Average MCQ Find Monthly Income for Average »
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Top 149+ Aptitude Average on Cricket & Exam MCQ Test Quiz »
The following question based on average topic of quantitative aptitude
(a) 0
(b) 45
(c) 47.5
(d) 50
The correct answers to the above question in:
Answer: (a)
Marks obtained by eleventh candidate
= 22 × 45 – (10 × 55 + 11 × 40)
= 990 – (550 + 440)
= 990 – 990 = 0
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Read more new average from error Based Quantitative Aptitude Questions and Answers
Question : 1
The average marks of 100 students were found to be 40. Later on it was discovered that a score of 53 was misread as 83. Find the correct average corresponding to the correct score.
a) 39
b) 38.7
c) 41
d) 39.7
Answer »Answer: (d)
Total of correct marks = 100 × 40 – 83 + 53 = 3970
∴ Correct average marks = $3970/100$ = 39.70
Aliter : Using Rule 26,
If average of n numbers is m later on it was found that a number 'a’ was misread as 'b’.
The correct average will be = m +${\text"(a-b)"}/ \text"n"$.
Here, n = 100, m = 40
a = 53, b = 83
Correct Average = m +${\text"(a-b)"}/ \text"n"n$
= 40 +$({53-83}/100)$
= 40- $30/100$ = 39.70
Question : 2
The average weight of a group of 20 boys was calculated to be 89.4 kg and it was later discovered that one weight was misread as 78 kg. instead of 87kg. The correct average weight is
a) 89.25 kg
b) 88.95 kg
c) 89.85 kg
d) 89.55 kg
Answer »Answer: (c)
Difference in weight = 87 – 78 = 9 kg
∴ Correct average weight = 89.4 + $9/20$
= 89.4 + 0.45 = 89.85 kg
Aliter : Using Rule 26,
If average of n numbers is m later on it was found that a number 'a’ was misread as 'b’.
The correct average will be = m +${\text"(a-b)"}/ \text"n"$.
Here, n = 20, m = 89.4
a = 87, b = 78
Correct Average = m + ${\text"(a-b)"}/ \text"n"n$
= 89.4+${(87-78)}/20$
= 89.4 + $9/20$
= 89.4 + 0.45 = 89.85 kg
Question : 3
The average weight of 15 students in a class increases by 1.5kg when one of the students weighing 40 kg is replaced by a new student. What is the weight (in kg) of the new student ?
a) 56 kg.
b) 64.5 kg.
c) 62.5 kg.
d) 60 kg.
Answer »Answer: (c)
Weight of the new student
= (40 + 15 × 1.5) kg
= (40 + 22.5) kg
= 62.5 kg
Aliter : Using Rule 18,
If in the group of N persons, a new person comes at the place of a person of 'T’ years, so that average age,
increases by 't’ years
Then, the age of the new person = T + N.t.
Here, N = 15, T = 40, t = 1.5
Weight of new Person = T + Nt
= 40 + 15 × 1.5
= 40 + 22.5
= 62.5 kg.
Question : 4
In an examination, the average of marks was found to be 50. For deducting marks for computational errors, the marks of 100 candidates had to be changed from 90 to 60 each and so the average of marks came down to 45. The total number of candidates, who appeared at the examination, was
a) 300
b) 600
c) 150
d) 200
Answer »Answer: (b)
Let total number of candidates be x.
∴ 50x – 30 × 100 = 45x
⇒ 5x = 3000
⇒ x = $3000/5$=600
Question : 5
A student, by mistake, wrote 64 in place of 46 as a number at the time of finding the average of 10 given numbers and got the average as 50. The correct average of the numbers is :
a) 48
b) 48.2
c) 49
d) 48.1
Answer »Answer: (b)
Correct sum of numbers
= 10 × 50 – 64 + 46
= 500 – 18 = 482
∴ Correct average = $482/10$ = 48.2
Question : 6
The average of 20 numbers is calculated as 35. It is dicovered later, that while calculating the average, one number, namely 85, was read as 45. The correct average is
a) 37
b) 36.5
c) 36
d) 37.5
Answer »Answer: (a)
Correct sum of 20 numbers
= 20 × 35 – 45 + 85
= 700 + 40 = 740
∴ Correct average = $740/20$ = 37
Aliter : Using Rule 26,
If average of n numbers is m later on it was found that a number 'a’ was misread as 'b’.
The correct average will be = m +${\text"(a-b)"}/ \text"n"$.
Here, n = 20, m = 35
a = 85, b = 45
Correct mean = m + ${\text"(a - b)"}/\text"n"$
= 35 +${(85 - 45)}/20$
= 35 + 2 = 37
GET average PRACTICE TEST EXERCISES
model 1 basic average questions
model 2 average of consecutive numbers
model 3 twice, thrice, one third etc. of numbers
model 4 find nth average from 1st & last number
model 5 find new average from error
model 6 find average of excluded number
model 7 average on ages/weight
model 8 find monthly income
model 9 average on cricket/exam
average Shortcuts and Techniques with Examples
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model 1 basic average questions
Defination & Shortcuts … -
model 2 average of consecutive numbers
Defination & Shortcuts … -
model 3 twice, thrice, one third etc. of numbers
Defination & Shortcuts … -
model 4 find nth average from 1st & last number
Defination & Shortcuts … -
model 5 find new average from error
Defination & Shortcuts … -
model 6 find average of excluded number
Defination & Shortcuts … -
model 7 average on ages/weight
Defination & Shortcuts … -
model 8 find monthly income
Defination & Shortcuts … -
model 9 average on cricket/exam
Defination & Shortcuts …
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