Average test 7-Solved questions with detailed explanations for SSC, IBPS, SBI PO, RRB, RBI, CSE, CGL, CHSL, CDA, CSE, UPSC

6)

The average cost of 5 books and 4 pens is ₹ 36. The average cost of 7 books and 8 pens? is ₹ 48. Find the cost of 12 books and 12 pens together?

A)
₹ 1016
B)
₹ 1044
C)
₹ 1020
D)
Cannot be determined
E)
None of these

Answer: Option B

Explanation

Given,

Average cost of 5 books and 4 pens = ₹ 36

Average cost of 7 books and 8 pens = ₹ 48

We know the formula,

$Average (A) = \frac{Sum of given values (S)}{Total number of values (N)}$

Sum of average cost of 5 books and 4 pens (A=36, N=9)

S= A×N

=36 × 9= 324

Sum of average cost of 7 books and 8 pens (A=48, N=15)

S= A×N

=48× 15= 720

∴ Total cost of 12 books and 12 pens = 320+720

= 1044

Hence, Option B is correct.

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Discussion

7)

If two new students of weight 51.5 kg and 50 kg are joined, then the average becomes 54 kg in a class. Find the number of students in the beginning?

A)
6
B)
5
C)
8
D)
4
E)
Cannot be determined

Discussion

8)

The average of 30 observations is 45. If three new observations 42, 44 and 48 be added, then find the new average?

A)
42.9
B)
42.1
C)
42.4
D)
42.6
E)
None of these

Answer: Option E

Explanation

Given,

Average cost of 5 books and 4 pens = ₹ 36

Average cost of 7 books and 8 pens = ₹ 48

We know the formula,

$Average (A) = \frac{Sum of given values (S)}{Total number of values (N)}$

Sum of average 30 observations s 45 (A=45, N=30)

S= A×N

S=45× 30= 1350

Sum of 3 new average 42, 44, 48 are added (A=45, N=33, S=1484)

$A = \frac{S}{N} = \frac{1350 + 42 + 44 + 48}{33} = \frac{1484}{33}$

= 44.9

Hence, Option E is correct.

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Discussion

9)

The average age of a class of 45 girls is 16 yr. The average age of 15 of them was 12 yr and another 10 was 14 yr. Find the average age of the remaining girls?

A)
20 yr
B)
18 yr
C)
21 yr
D)
24 yr
E)
None of these

Answer: Option A

Explanation

Given,

Total Average age of 45 girls is 16 yr = 45 × 16

=720

The Average age of 15 girls is 12 yr = 15 × 12

= 180

The Average age of 10 girls is 14 yr = 10 × 14

= 140

∴ The average age of the remaining girls

$= \frac{720 - 180 - 140}{20} = \frac{400}{20}$

=20 yr

Hence, Option A is correct.

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Discussion

10)

Sum of three consecutive even numbers is 68 more than the average of the numbers. Find the middle number?

A)
30
B)
34
C)
32
D)
36
E)
None of these

Answer: Option B

Explanation

Let three consecutive even numbers be x, x+2, x+4

According to the question

$= x + x + 2 + x + 4 - \frac{x + x + 2 + x + 4}{3} = 68 = 3 x + 6 - \frac{3 x + 6}{3} = 68 = 3 x + 6 - \frac{3 (x + 2)}{3} = 68$

= 3x+6-x-2= 68

= 2x+4= 68

= 2x= 64

X=32

So, the 3 consecutive even numbers are

x =32

x+2=34

x+4 =36

The middle number = 34

Hence, Option B is correct.

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Discussion

Average Test-7 (Complete Revision)

Answer: Option B

Answer: Option E

Answer: Option E

Answer: Option A

Answer: Option B