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) 42
(b) 28
(c) 45
(d) 32
The correct answers to the above question in:
Answer: (a)
Correct sum of 9 observations
= 9 × 35 – 18 + 81
= 315 + 63 = 378
∴ Required correct average = $378/9$ = 42
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Read more new average from error Based Quantitative Aptitude Questions and Answers
Question : 1
The average of 25 observations is 13. It was later found that an observation 73 was wrongly entered as 48. The new average is
a) 14
b) 12.6
c) 13.8
d) 15
Answer »Answer: (a)
Difference of two observations = 73 – 48 = 25
∴ New average = 13 + $25/25$=14
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 = 25, m = 13
a = 73, b = 48
Correct Average = m + ${\text"(a-b)"}/ \text"n"n$
= 13 +${(73- 48)}/25$
= 13 + 1 = 14
Question : 2
In an exam, the average marks obtained by the students was found to be 60. After omission of computational errors, the average marks of 100 candidates had to be changed from 60 to 30 and the average with respect to all the examinees came down to 45 marks. The total number of candidates who took the exam, was
a) 210
b) 200
c) 180
d) 240
Answer »Answer: (b)
Let the number of candidates be x, then
60x – 45x = 30 × 100
⇒ 15x = 3000
⇒ x = 200
Question : 3
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
Question : 4
The average of 50 numbers is 38. If two numbers, namely 45 and 55 are discarded, the average of the remaining numbers is
a) 37.9
b) 37.5
c) 37.0
d) 36.5
Answer »Answer: (b)
Sum of 50 numbers = 50 × 38 = 1900
Sum of 48 numbers = 1900 – 45 – 55 = 1800
∴ Required average = $1800/48$ = 37.5
Question : 5
The average weight of 20 students in a class is increased by 0.75 kg when one of the students weighing 30 kg is replaced by a new student. Weight of the new student (in kg) is :
a) 40
b) 35
c) 50
d) 45
Answer »Answer: (d)
Required answer = 30 + 20 × 0.75
= 30 kg + 15 kg = 45 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 = 20, T = 30, t = 0.75
Weight of New student = T + Nt
= 30 + 20 × 0.75
= 30 + 15 = 45 kg
Question : 6
There are 50 students in a class. One of them weighing 50 kg goes away and a new student joins. By this the average weight of the class increases by $1/2$ kg. The weight of the new student is :
a) 72 kg
b) 70 kg
c) 76 kg
d) 75 kg
Answer »Answer: (d)
Total weight increased =$1/2$ × 50 = 25 kg.
∴ Weight of the new man = 50 + 25 = 75 kg.
Aliter : Using Rule 18,The age of the new person = T + N.t.
Here, N = 50, T = 50, t = $1/2$
Weight of New boy = T + Nt
= 50 + 50 × $1/2$ = 75 kg.
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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