Average test 3-Solved questions with detailed explanations for SSC, IBPS, SBI PO, RRB, RBI, CSE, CGL, CHSL, CDA, CSE, UPSC

11)

The average age of 4 members of a family is 25 yr. If head of the family is included in this group, then average age increases by 20%. Find out the age of the head?

A)
45 yr
B)
50 yr
C)
55 yr
D)
60 yr
E)
None of these

Answer: Option B

Explanation

Here we can use the formula

$Average (A)= \frac{Sum of observations (S)}{No . of observations (N)} ⇒ S=A×N$

According to the question,

Sum of 4 members age (A=25, N=4)

⇒S=25 X 4 =100

Later, Head of the family included, Average increases by 20% (so A=30, N=5)

So, sum of 5 members age

⇒S=30 X 5 =150-100

Now,

The age of the head =(sum of 4 members age)-(Sum of 5 members age)

=150-100

=50 yr.

Hence, Option B is correct.

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Discussion

12)

The average height of 27 persons was recorded as 162 cm. If the height of Shreyas was deleted from the observation, the average height reduced by 1 cm. What was Shreya's height?

[IBPS/RRB, 2012]

A)
184 cm
B)
226 cm
C)
179 cm
D)
186 cm
E)
None of these

Answer: Option E

Explanation

Here we can use the formula

$Average (A)= \frac{Sum of observations (S)}{No . of observations (N)} ⇒ S=A×N$

According to the question,

Sum of height of 27 persons (A=162, N=27)

⇒S=162 X 27 =4374

Later, Shreya's height was deleted, the average height reduced by 1 cm. (so A=161, N=26)

So, sum of height of 26 persons

⇒S=161 X 26 =4186

Now,

Shreya's height =(sum of height of 27 persons)-(Sum of height of 26 persons)

=4374-4186

=188 cm.

Hence, Option E is correct.

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Discussion

13)

The average age of 14 girls and their teacher's age is 15 yr. If teacher's age is excluded, then the average reduced by 1. What is the teacher's age?

[IBPS (PO), 2012]

A)
29 yr
B)
35 yr
C)
32 yr
D)
30 yr
E)
None of these

Answer: Option A

Explanation

Here we can use the formula

$Average (A)= \frac{Sum of observations (S)}{No . of observations (N)} ⇒ S=A×N$

According to the question,

Sum of 15 members age (A=15, N=15)

⇒S=15 X 15 =225

Later, the teachers age is excluded, the average reduced by 1 yr. (so A=14, N=14)

So, sum of 14 girls age

⇒S=14 X 14 =196

Now,

The Teacher's age =(sum of 15 members age)-(Sum of 14 girls age)

=225-196

=29 yr.

Hence, Option A is correct.

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Discussion

14)

The mean weight of 34 students of a school is 42 kg. If the weight of the teacher is included, then the mean rises by 400 g. Find the weight (in kg) of the teacher?

[RRB, 2015]

A)
66
B)
56
C)
55
D)
57
E)
None of these

Answer: Option B

Explanation

Here we can use the formula

$Average (A)= \frac{Sum of observations (S)}{No . of observations (N)} ⇒ S=A×N$

According to the question,

Sum of weight of 34 students (A=42, N=34)

⇒S=42 X 34 =1428

Later, Wieght of the teacher included, The mean rises by 400 g. (so A=42.4, N=35)

So, sum of weight of 35 students

⇒S=42.4 X 35 =1484

Now,

The teacher's age =(sum of weight of 34 students)-(Sum of weight of 35 students)

=1484-1428

= 56

Hence, Option B is correct.

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Discussion

15)

The average weight of 21 boys was recorded as 64 kg. If the weight of the principal was added, the average increased by 1 kg. What was the principal's weight?

[IBPS (PO), 2015]

A)
86 kg
B)
64 kg
C)
72 kg
D)
98 kg
E)
None of these

Answer: Option A

Explanation

Here we can use the formula

$Average (A)= \frac{Sum of observations (S)}{No . of observations (N)} ⇒ S=A×N$

According to the question,

Sum of weight of 21 boys (A=64, N=21)

⇒S=64 X 21 =1344

Later, Wieght of the principal is added, the average increases by 1 kg. (so A=65, N=22)

So, sum of 21 boys and principal weight is

⇒S=65 X 22 =1430

Now,

The principal's weight =(sum of weight of 21 boys)-(Sum of 21 boys and principal weight)

= 1430-1344

= 86 kg.

Hence, Option A is correct.

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Discussion

Average Test-3 (Addition or Elimination of Items)

Answer: Option B

Answer: Option E

Answer: Option A

Answer: Option B

Answer: Option A