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 : 31
A student was asked to find the arithmetic mean of the following 12 numbers : 3, 11, 7, 9, 15, 13, 8, 19, 17, 21, 14 and x He found the mean to be 12. The value of x will be :
a) 17
b) 31
c) 7
d) 3
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
Mean = ${3 +11+ 9+7+15+ 13+ 8 +19 +17 +21 +14+x}/12$
According to question,
${137+x}/12$ = 12
∴ 137 + x = 144
∴ x = 144 – 137 = 7
Question : 32
The average of 100 observations was calculated as 35. It was found later, that one of the observations was misread as 83 instead of 53. The correct average is :
a) 35.7
b) 36.7
c) 34.7
d) 32.7
Answer »Answer: (c)
Difference = 83 – 53 = 30
Incorrect observation > Correct observation
∴ Required average
= 35 - $30/100$ = 35 – 0.3 = 34.7
Question : 33 [SSC CGL Tier-II 2015]
Three Science classes A, B and C take a Life Science test. The average score of class A is 83. The average score of class B is 76. The average score of class C is 85. The average score of class A and B is 79 and average score of class B and C is 81. Then the average score of classes A, B and C is
a) 80.5
b) 80
c) 81
d) 81.5
Answer »Answer: (d)
Using Rule 10,
If the average of '$n_1$' numbers is $a_1$ and the average of '$n_2$' numbers is $a_2$, then average of total numbers $n_1$ and $n_2$ is
$Average = {n_1a_1 + n_2a_2}/{n_1 + n_2}$
Students in class A ⇒ x
Students in class B ⇒ y
Students in class C ⇒ z
For classes A and B,
${83x + 76y}/{x+y}$ = 79
⇒ 83x + 76y = 79x + 79y
⇒ 83x – 79x = 79y – 76y
⇒ 4x = 3y
For classes B and C
${76y+85z}/{y+z}$= 81
⇒ 76y + 85z = 81y + 81z
⇒ 5y = 4z
∴ 20x = 15y = 12z
⇒ ${20x}/60$ = ${15y}/60$ = ${12z}/60$
⇒ $x/3$ = $y/4$ = $z/5$
∴ Required average
${83×3+76×4+85×5}/{3+4+5}$
${249+304+425}/12$ = $978/12$
= 81.5
Question : 34
Out of 20 boys, 6 are each of 1 m 15 cm height, 8 are of 1 m 10 cm and rest of 1 m 12 cm. The average height of all of them is
a) 1 m 21 cm
b) 1 m 12 cm
c) 1 m 21.1 cm
d) 1 m 12.1 cm
Answer »Answer: (d)
Using Rule 2,
If the given observations (x) are occuring with certain frequency (A) then,
$Average = {A_1x_1+A_2x_2+...............+A_nx_n}/{x_1+x_2+......+x_n}$
where, $A_1, A_2, A_3, .......... A_n$ are frequencies
Average height
= ${6×1.15+8×1.1+6×1.12}/20$
= ${6.9+8.8+6.72}/20$ = ${22.42}/20$
= 1 metre 12.1 cm
Question : 35 [SSC CHSL2012]
A library has an average number of 510 visitors on Sunday and 240 on other days. The average number of visitors per day in a month of 30 days beginning with Sunday is :
a) 300
b) 290
c) 295
d) 285
Answer »Answer: (d)
That month will have 5 sundays.
∴ Required average
= ${5×510+25×240}/30$
= ${2550+6000}/30$
= $8550/30$ = 285
Aliter : Using Rule 10,
Here, $n_1$ = 5, $a_1$ = 510
$n_2$ = 25, $a_2$ = 240
IMPORTANT quantitative aptitude EXERCISES
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Basic Average Questions Practice Test, Shortcuts, Tricks, PDF »
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Top 99+ Aptitude Average on Ages & Weights MCQ Test Quiz »
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Top 149+ Aptitude Average on Cricket & Exam MCQ Test Quiz »
model 1 basic average questions Shortcuts »
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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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