model 1 basic average questions 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 : 1 [S.S.C. (CHSL) 2011]
The average of x numbers is y and average of y numbers is x. Then the average of all the numbers taken together is
a) $\text"x+y"/\text"2xy"$
b) $\text"2xy"/\text"x+y"$
c) $(x^2+y^2)/\text"x+y"$
d) $\text"xy"/\text"x+y"$
Answer »Answer: (b)
Sum of x numbers = xy
Sum of y numbers = xy
∴ Required average = ${xy+xy}/{x+y}$ = ${2xy}/{x+y}$
Aliter : Using Rule 10,
Here, $n_1$ = x, $a_1$ = y
$n_2$ = y, $a_2$ = x
∴ Average = ${n_1a_1+n_2a_2}/{n_1+n_2}$
= ${xy+yx}/{x+y}$ = ${2xy}/{x+y}$
Question : 2 [S.S.C. (CISF) 2011]
If average of 20 observations x_{1},x_{2}, ....., x_{20} is y, then the average of x_{1} – 101, x_{2} – 101, x_{3} –101, ....., x_{20} –101 is
a) y20
b) y101
c) 20y
d) 101y
Answer »Answer: (b)
${X_1 + X_2 + X_3 + X_4 + ..... + X_20}/20 = Y$
$X_1 + X_2 + X_3 + X_4 + ..... + X_20 = 20Y$
$= {X_1  101 + X_2  101 + X_3  101 + X_4  101 + ..... + X_20  101}/20$
$= (X_1 + X_2 + X_3 + X_4 + ..... + X_20)  20 x 101/20$
$\text"20Y  20 x 101"/20$
= Y  101
Question : 3 [S.S.C. (CHSL) 2011]
The average of $x$ numbers is $y^2$ and the average of $y$ numbers is $x^2$. So the average of all the numbers taken together is
a) $(x^3+y^3)/\text"x+y"$
b) $xy$
c) $(x^2+y^2)/\text"x+y"$
d) $xy^2+yx^2$
Answer »Answer: (b)
According to the question,
Average of x number is y^{2}
∴ Sum of x number is = xy^{2}
Average of y number is = x^{2}
∴ Sum of y number is = yx^{2}
Average of all number is
= ${xy^2+yx^2}/{x+y}$
= ${xy(x+y)}/{x+y}$
= xy
Question : 4 [S.S.C. (CGL) 2016]
In a class, average height of all students is ‘a’ cms. Among them, average height of 10 students is ‘b’ cms and the average height of the remaining students is ‘c’ cms. Find the number of students in the class. (Here a > c and b > c )
a) $(a(bc))/(ac)$
b) $(bc)/(ac)$
c) $(bc)/\text"10(ac)"$
d) $\text"10(bc)"/(ac)$
Answer »Answer: (d)
Let the total number of students in the class be n.
According to the question,
an = 10 × b + (n – 10) c
⇒ an = 10b + nc – 10c
⇒ an – cn = 10b – 10c
⇒ n (a – c) = 10 (b – c)
$⇒ n =\text"10 (b  c )"/ ( a  c )$
Question : 5 [S.S.C. (CGL) 2015]
Average of n numbers is a. The first number is increased by 2, second one is increased by 4, the third one is increased by 8 and so on. The average of the new numbers is
a) $a+(2^(n1)1)/n$
b) $a+2(2^n1)/n$
c) $a+2^(n1)/n$
d) $a+(2^n1)/n$
Answer »Answer: (b)
Sum of new numbers
= na + (2 + 4 + 8 + 16 ..... to n terms)
Now, S = 2 + 4 + 8 + 16 + ..... to n terms
Here, a = first term = 2
r = common ratio = $4/2$ = 2
It is a geometric series.
∴ S =${a({r^n}  1)}/{r1}$= ${2({2^n}  1)}/{21}$
= 2 ($2^n$ –1)
∴ Required average
= ${na +2({2^n}1)}/n$
a +${2({2^n}1)}/n$
IMPORTANT quantitative aptitude EXERCISES

Basic Average Questions Practice Test, Shortcuts, Tricks, PDF »

New Average Aptitude MCQ Average of Consecutive Numbers »

Top 99+ Average Aptitude: Twice, One Third of Numbers MCQ »

New +99 Average Aptitude MCQ Find nth Average of Numbers »

99+ Average Aptitude Find New Average from Error MCQ Test »

Top 99+ Aptitude MCQ Test on Average With Excluded Number »

Top 99+ Aptitude Average on Ages & Weights MCQ Test Quiz »

Top Aptitude Average MCQ Find Monthly Income for Average »

Top 149+ Aptitude Average on Cricket & Exam MCQ Test Quiz »
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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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