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Q:

A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively. What is the speed of the train ?

A) 69.5 km/hr B) 70 km/hr
C) 79 km/hr D) 79.2 km/hr
 
Answer & Explanation Answer: D) 79.2 km/hr

Explanation:

Let the length of the train be x metres and its speed by y m/sec.


Then, x/y = 8 => x = 8y


Now, (x+264)/20 = y
8y + 264 = 20y
y = 22.
Speed = 22 m/sec = (22*18/5) km/hr = 79.2 km/hr.

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Filed Under: Problems on Trains

Q:

A 270 metres long train running at the speed of 120 kmph crosses another train running in opposite direction at the speed of 80 kmph in 9 seconds. What is the length of the other train ?

A) 230 m B) 240 m
C) 260 m D) 320 m
 
Answer & Explanation Answer: A) 230 m

Explanation:

Relative speed = (120 + 80) km/hr


=(200*5/18)m/s = (500/9)m/s

 

Let the length of the other train be x metres.

 

Then, x+270/9 = 500/9 

 

=>  x + 270 = 500

 

=>  x = 230.

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Filed Under: Problems on Trains

Q:

0.1 decates ago, Vijaya was quadrice as old as her daughter Simran. 0.6 decades hence, Vijaya’s age will beat her daughter’s age by 0.9 decades. The proportion of the current ages of Vijaya and Simran is : [ 0.1 Decates =1 Year; quadrice = 4 times]

A) 8:1 B) 10:2
C) 11:4 D) 13:4
 
Answer & Explanation Answer: D) 13:4

Explanation:

Let, Ages of Vijaya and Simran – 1 year ago was 4A and A years correspondingly.
Then, [(4A + 1) + 6] – [(A + 1) + 6] = 9
3A = 9  => A = 3

 

Needed Ratio = (4A + 1) : (A + 1) = 13 : 4

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Filed Under: Problems on Ages

Q:

If two times of the daughter’s age in years is included to the mother’s age, the total is 70 and if two times of the mother’s age is included to the daughter’s age, the total is 95. So the Mother’s age is,

A) 30 B) 38
C) 40 D) 41
 
Answer & Explanation Answer: C) 40

Explanation:

Let daughter’s age = A and mother’s age = B
Given: 2A+B = 70 and A+2B = 95
Solving B, we will get B = 40.

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Filed Under: Problems on Ages

Q:

The ratio of the ages of Maala and Kala is 4 : 3. The total of their ages is 2.8 decades. The proportion of their ages after 0.8 decades will be [1 Decade = 10 years]

A) 4:3 B) 12:11
C) 7:4 D) 6:5
 
Answer & Explanation Answer: D) 6:5

Explanation:

Let, Maala’s age = 4A and Kala’s age = 3A
Then 4A + 3A = 28
A = 4
Maala’s age = 16 years
and Kala’s age = 12 years
Proportion of their ages after 8 is = (16 + 8) : (12 + 8)
= 24 : 20
= 6 : 5

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Filed Under: Problems on Ages

Q:

The age of a person is thrice the total ages of his 2 daughters. 0.5 decades hence, his age will be twice of the total ages of his daughters. Then what is the father’s current age? [0.5 Decades = 5 Years]

A) 35 years B) 40 years
C) 45 years D) 47 years
 
Answer & Explanation Answer: C) 45 years

Explanation:

Let, Total of current ages of the 2 daughters is A years.
Then, father’s current age = 3A years.
(3A + 5) = 2 (A +10)
3A + 5 = 2A + 20
A = 15
Therefore, father’s current age = 45 years.

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Filed Under: Problems on Ages

Q:

If 47. 2506 = 4*A + 7/B + 2*C + 5/D + 6*E, then the value of 5*A + 3*B + 6*C + D + 3*E is :

A) 55.6003 B) 53.603
C) 153.6003 D) 213.003
 
Answer & Explanation Answer: C) 153.6003

Explanation:

4*A + 7/B + 2*C + 5/D + 6*E =47.2506
=> 4 * A + 7/B + 2 *C + 5/D + 6*E = 40 + 7 + 0.2 + 0.05 + 0.0006
Comparing the terms on both sides, we get :
4*A =40, 7/B = 7, 2*C = 0.2, 5/D = 0.05, 6*E = 0.0006
A = 10,
B = 1,
C = 0.1,
D = 100,
E = 0.0001.
5*A + 3*B + 6*C + D + 3*E =(5*10) + (3*1) + (6*0.1) +100 +(3*0.0001)
=50 + 3 + 0.6 + 100 + 0.003 = 153.6003.

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Filed Under: Decimal Fractions

Q:

The difference between a positive proper fraction and its reciprocal is 9 / 20. Then the fraction is :

A) 3/5 B) 3/10
C) 4/5 D) 5/4
 
Answer & Explanation Answer: C) 4/5

Explanation:

Let the required fraction be x. Then, (1 / x )- x = 9/20
1 - x^(2) / x = 9 / 20  =>  20 - 20 * x^(2) = 9 * x.
20 * x^(2) + 9 *x - 20 = 0.
=> (4 * x + 5) (5 * x - 4) = 0.
=> x = 4 / 5.

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Filed Under: Numbers