Average test 4-Solved questions with detailed explanations for SSC, IBPS, SBI PO, RRB, RBI, CSE, CGL, CHSL, CDA, CSE, UPSC

21)

The average marks of 100 students were found to be 40. Later on it was discovered that a score of 53 was misread as 83. The correct average corresponding to the correct score is?

A)
38.7
B)
39
C)
39.7
D)
41
E)
None of these

Answer: Option C

Explanation

Given,

Average marks of 100 students were found to be 40

Sum of observation

=100×40= 4000

Later on it was discovered that a score of 53 was misread as 83.

(Correct score= Sum of observation+ correct score- incorrect score)

The correct marks of 100 students

= 4000+53-83= 3970

∴ Required average = $\frac{3970}{100}$ = 39.7

Hence, Option C is correct.

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Discussion

22)

To find the average of five numbers, a student write a number 54 inspite of 45. Thus, the average of these numbers is 52. The correct average of these numbers is?

A)
50.4
B)
50.2
C)
50.1
D)
50
E)
None of these.

Discussion

23)

The mean of 12 observations is 30. by error, one observation was noted as 12, but was misread as 21. What is the correct mean?

A)
29.25
B)
25.3
C)
33
D)
45.62
E)
None of these

Discussion

24)

The average marks in physics lab of a class of students is 55. If the marks of two students were 28 and 25 ofthe actual marks 45 and 50 respectively, then what would be the correct average?

A)
45
B)
85
C)
95
D)
55
E)
None of these

Answer: Option D

Explanation

According to the question

Sum of the added quantities - Sum of removed quantities= ±Nx

⇒(45+50)-(28+25)=±42×x

⇒ 95-53= 42×x

⇒ x= $\frac{20}{20}$ =1

∴ The correct average= 55+1 =56

Hence, Option D is correct.

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Discussion

25)

The average marks in biology subject of a class of 24 students is 56. if the marks of three students were misread as 44, 45 and 61 of the actual marks 48, 59 and 67 respectively, then what would be the correct average?

A)
56
B)
55
C)
57.5
D)
45.82
E)
None of these

Answer: Option E

Explanation

According to the question,

We know the formula,

Sum of the added quantities - Sum of removed quantities= ±Nx

⇒ (44+45+61)-(48+59+67)= -24x

⇒ 150-174= -24x

⇒ x= $\frac{- 24}{- 24}$ =1

∴ The correct average= 56+1 =57

Hence, Option D is correct.

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Discussion

Average Test-4 (Calculating average after replacement of data)

Answer: Option C

Answer: Option B

Answer: Option A

Answer: Option D

Answer: Option E