model 4 find nth average from 1st & last number 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) 18
(b) 25
(c) 20
(d) 19
The correct answers to the above question in:
Answer: (b)
Using Rule 1,
Average of two or more numbers/quantities is called the mean of these numbers, which is given by
$\text"Average(A)" = \text"Sumof observation / quantities"/\text"No of observation / quantities"$
∴ S = A × n
a + b + c = 18 × 3 = 54
and, b + c + d = 16 × 3 = 48
∴ a + b + c – b – c – d
⇒ 54 – 48 = 6
⇒ a – d = 6
⇒ a – 19 = 6
⇒ a = 19 + 6 = 25
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Read more find nth term Based Quantitative Aptitude Questions and Answers
Question : 1
The average of 30 numbers is 12. The average of the first 20 of them is 11 and that of the next 9 is 10. The last number is
a) 45
b) 50
c) 40
d) 60
Answer »Answer: (b)
Using Rule 1,
Average of two or more numbers/quantities is called the mean of these numbers, which is given by
$\text"Average(A)" = \text"Sumof observation / quantities"/\text"No of observation / quantities"$
∴ S = A × n
Last number
= 30 × 12 – 20 × 11 – 9 × 10
= 360 – 220 – 90
= 360 – 310 = 50
Question : 2
The average of 15 numbers is 7. If the average of the first 8 numbers be 6.5 and the average of last 8 numbers be 9.5, then the middle number is
a) 21
b) 18
c) 23
d) 20
Answer »Answer: (c)
Using Rule 1,
The middle number
= 8 × 6.5 + 8 × 9.5 – 15 × 7
= 52 + 76 – 105
= 128 – 105 = 23
Question : 3
The average of 9 numbers is 30. The average of first 5 numbers is 25 and that of the last 3 numbers is 35. What is the 6th number?
a) 30
b) 50
c) 40
d) 20
Answer »Answer: (c)
Using Rule 1,
Average of two or more numbers/quantities is called the mean of these numbers, which is given by
$\text"Average(A)" = \text"Sumof observation / quantities"/\text"No of observation / quantities"$
∴ S = A × n
According to question,
The average of 9 numbers = 30
Now,The total of 9 numbers
= 30 × 9 = 270
The average of first 5 numbers = 25
∴ The total of first 5 numbers = 25 × 5 = 125
and Total of last 3 numbers = 3 × 35 = 105
Hence, required answer
= 270 – (125 + 105)
= 270 – 230 = 40
Question : 4
Out of seven given numbers, the average of the first four numbers is 4 and that of the last four numbers is also 4. If the average of all the seven numbers is 3, fourth number is
a) 4
b) 11
c) 7
d) 3
Answer »Answer: (b)
Using Rule 1,
Average of two or more numbers/quantities is called the mean of these numbers, which is given by
$\text"Average(A)" = \text"Sumof observation / quantities"/\text"No of observation / quantities"$
∴ S = A × n
Fourth number
= (4×4+4×4 – 3×7)
= (16 +16-21) = 11
Question : 5
Out of four numbers, the average of the first three is 15 and that of the last three is 16. If the last number is 19, the first is
a) 15
b) 18
c) 16
d) 19
Answer »Answer: (c)
Using Rule 1,
a + b + c = 45 and
b + c + d = 48
⇒ b + c = 48 – 19 = 29
∴ a + b + c = 45
⇒ a = 45 – 29 = 16
Question : 6
The mean of 11 numbers is 35. If the mean of first 6 numbers is 32 and that of the last 6 numbers is 37, find the sixth number.
a) 29
b) 27
c) 30
d) 28
Answer »Answer: (a)
Using Rule 1,
Average of two or more numbers/quantities is called the mean of these numbers, which is given by
$\text"Average(A)" = \text"Sum of observation / quantities"/\text"No of observation / quantities"$
∴ S = A × n
Sixth number
= 6 × 32 + 6 × 37 – 11 × 35
= 192 + 222 – 385 = 29
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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