In a certain school, 20% of students are below 8 years of age. The number of students above 8 years of age is of the number of students of 8 years of age which is 48. What is the total number of students in the school?

Byadmin July 18, 2022

Question: In a certain school, 20% of students are below 8 years of age. The number of students above 8 years of age is of the number of students of 8 years of age which is 48. What is the total number of students in the school?
[A].

[B].

[C].

120

[D].

150

Answer: Option E

Explanation:

Let the number of students be x. Then,

Number of students above 8 years of age = (100 – 20)% of x = 80% of x.

80% of x = 48 +	2	of 48
	3

	80	x = 80
	100

x = 100.

Video Explanation: https://youtu.be/yPfocU6DA2M

Compound Interest | Mathematics Mcqs

How much would a sum of Rs 16000 approximately amount to in 2 years at 10% P.a compounded half-yearly?

How much would a sum of Rs 16000 approximately amount to in 2 years at 10% P.a compounded half-yearly?

A. Rs 17423
B. Rs 18973
C. Rs 19448
D. Rs 19880
Explanation:
P = Rs 16000, R = (10/2)%
Per half-year , t= 4 half-years
Therefore Amount = Rs [16000 × (1+5/100)4]
= Rs (16000 × 21/20 × 21/20 × 21/20 × 21/20)
= Rs 1448.10 ~ Rs 19448

Read More How much would a sum of Rs 16000 approximately amount to in 2 years at 10% P.a compounded half-yearly?
Aptitude | Surds And Indices

If m and n are whole numbers such that mn = 121, the value of (m – 1)n + 1 is:

Question:
If m and n are whole numbers such that mn = 121, the value of (m – 1)n + 1 is:

[A].

1
[B].
10
[C].
121
[D].
1000

Answer: Option D

Explanation:

We know that 112 = 121.

Putting m = 11 and n = 2, we get:

(m – 1)n + 1 = (11 – 1)(2 + 1) = 103 = 1000.

Read More If m and n are whole numbers such that mn = 121, the value of (m – 1)n + 1 is:
Aptitude | Compound Interest

The effective annual rate of interest corresponding to a nominal rate of 6% per annum payable half-yearly is:

Question:
The effective annual rate of interest corresponding to a nominal rate of 6% per annum payable half-yearly is:

[A].

6.06%
[B].
6.07%
[C].
6.08%
[D].
6.09%

Answer: Option D

Explanation:

Amount of Rs. 100 for 1 year
when compounded half-yearly = Rs. 100 x 1 + 3 2 = Rs. 106.09

100

Effective rate = (106.09 – 100)% = 6.09%

Read More The effective annual rate of interest corresponding to a nominal rate of 6% per annum payable half-yearly is:
Aptitude | Pipes And Cistern

Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill the cistern. How much time will be taken by A to fill the cistern separately?

Question:
Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill the cistern. How much time will be taken by A to fill the cistern separately?

[A].

1 hour
[B].
2 hours
[C].
6 hours
[D].
8 hours

Answer: Option C

Explanation:

Let the cistern be filled by pipe A alone in x hours.

Then, pipe B will fill it in (x + 6) hours.

1 + 1 = 1

x (x + 6) 4

x + 6 + x = 1

x(x + 6) 4

x2 – 2x – 24 = 0

(x -6)(x + 4) = 0

x = 6. [neglecting the negative value of x]

Read More Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill the cistern. How much time will be taken by A to fill the cistern separately?
Aptitude | Average

The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:

Question:
The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:

[A].

17 kg
[B].
20 kg
[C].
26 kg
[D].
31 kg

Answer: Option D

Explanation:

Let A, B, C represent their respective weights. Then, we have:

A + B + C = (45 x 3) = 135 …. (i)

A + B = (40 x 2) = 80 …. (ii)

B + C = (43 x 2) = 86 ….(iii)

Adding (ii) and (iii), we get: A + 2B + C = 166 …. (iv)

Subtracting (i) from (iv), we get : B = 31.

B’s weight = 31 kg.

Read More The average weight of A, B and C is 45 kg. If the average weight of A and B be 40 kg and that of B and C be 43 kg, then the weight of B is:
Aptitude | Problems On Trains

A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:

Question: A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:
[A].

45 km/hr
[B].
50 km/hr
[C].
54 km/hr
[D].
55 km/hr

Answer: Option B

Explanation:

Speed of the train relative to man = 125 m/sec

10

   = 25 m/sec.

2

   = 25 x 18 km/hr

2 5

   = 45 km/hr.

Let the speed of the train be x km/hr. Then, relative speed = (x – 5) km/hr.

x – 5 = 45 x = 50 km/hr.

Read More A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:

Amount of Rs. 100 for 1 year when compounded half-yearly		= Rs.		100 x		1 +	3		2		= Rs. 106.09
							100

	x + 6 + x	=	1
	x(x + 6)		4

Speed of the train relative to man =		125	m/sec
		10

=		25	m/sec.
		2

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