model 4 find nth average from 1st & last number Practice Questions Answers Test with Solutions & More Shortcuts
average PRACTICE TEST [9 - 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
Question : 21
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 : 22 [SSC CGL 2003]
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 : 23
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 : 24 [SSC CHSL DEO & LDC 2014]
Three numbers are such that the average of first two numbers is 2, the average of the last two numbers is 3 and the average of the first and the last numbers is 4, then the average of three numbers is equal to
a) 3.5
b) 2.5
c) 3
d) 2
Answer »Answer: (c)
Using Rule 1,
Numbers in order
⇒ a, b and c
∴ a + b = 2 × 2 = 4
b + c = 2 × 3 = 6
c + a = 2 × 4 = 8
On adding,
2 (a + b + c) = 4 + 6 + 8 = 18
⇒ a + b + c = $18/2$ = 9
∴ Required average =$9/3$ = 3
Question : 25 [SSC CHSL DEO & LDC 2010]
The average of eight successive numbers is 6.5. The average of the smallest and the greatest numbers among them will be :
a) 6.5
b) 9
c) 7.5
d) 4
Answer »Answer: (a)
Using Rule 1,
x + x + 1 + x + 2 + x + 3 + x + 4 + x + 5 + x + 6 + x + 7 = 6.5 × 8 = 52
⇒ 8x + 28 = 52
⇒ 8x = 52 – 28 = 24
⇒ x = 3
∴ Required average =${3+10}/2$= 6.5
IMPORTANT quantitative aptitude 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 »
model 4 find nth average from 1st & last number Shortcuts »
Click to Read...model 4 find nth average from 1st & last number Online Quiz
Click to Start..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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