GATE Questions

Q:

The top and bottom of a tower were seen to be at angles of depression 30° and 60° from the top of a hill of height 100 m. Find the height of the tower ?

A) 42.2 mts B) 33.45 mts
C) 66.6 mts D) 58.78 mts
 
Answer & Explanation Answer: C) 66.6 mts

Explanation:

ht1488353450.jpg image

From above diagram
AC represents the hill and DE represents the tower

Given that AC = 100 m

angleXAD = angleADB = 30° (∵ AX || BD )
angleXAE = angleAEC = 60° (∵ AX || CE)

Let DE = h

Then, BC = DE = h, AB = (100-h) (∵ AC=100 and BC = h), BD = CE

tan 60°=AC/CE => √3 = 100/CE =>CE = 100/√3 ----- (1)

tan 30° = AB/BD => 1/√3 = 100−h/BD => BD = 100−h(√3)
∵ BD = CE and Substitute the value of CE from equation 1
100/√3 = 100−h(√3) => h = 66.66 mts

The height of the tower = 66.66 mts.

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Filed Under: Height and Distance
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Q:

The compound interest on a certain sum for 2 years at 10% per annum is Rs. 1155. The simple interest on the same sum for double the time at half the rate percent per annum is ?

A) Rs. 1100 B) Rs. 5500
C) Rs. 1400 D) Rs. 4120
 
Answer & Explanation Answer: A) Rs. 1100

Explanation:

Let the sum be Rs.x. Then, 

 

 x1+101002-x=1155

 

x11102-1=1155

 

=> x =5500

 

sum = Rs. 5500.

 

So, S.I = Rs. 5500×5×4100 = 1100

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Filed Under: Compound Interest
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2 6382
Q:

A shopkeeper sells two articles at Rs.1000 each, making a profit of 20% on the first article and a loss of 20% on the second article. Find the net profit or loss that he makes?

A) 2% B) 4%
C) 3% D) 2.5%
 
Answer & Explanation Answer: B) 4%

Explanation:

SP of first article = 1000

Profit = 20%

CP = 100100+P×SP= 5000/6 = 2500/3


SP of second article = 1000

Loss = 20%

CP = 100100-L×SP= 5000/4 = 1250


Total SP = 2000

Total CP = 25003+ 1250 = 6250/3

CP is more than SP, he makes a loss.

Loss = CP-SP = (6250/3)- 2000 = 250/3


Loss Percent =250362503×100= 4%

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Filed Under: Profit and Loss
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5 6378
Q:

How long will it take for two pipes A and B to fill an empty cistern if they worked alternately for an hour each ?

A. Working alone, Pipe A can fill the cistern in 40 hours
B. Pipe B is one third as efficient as Pipe A

A) Only A is sufficient B) Only B is sufficient
C) Both (A) and (B) are sufficient D) None
 
Answer & Explanation Answer: C) Both (A) and (B) are sufficient

Explanation:

From statement A, we know that Pipe A can fill the tank in 40 hours. However, this information is not sufficient as we do not have the data for Pipe B. Hence, statement A alone cannot answer the given question.

From statement B, we know that Pipe B is one third as efficient as pipe A. However, we do not know the rate at which Pipe A fills the tank. Hence, we will not be able to find the rate at which Pipe B fills the cistern. Therefore, statement B alone is not sufficient to answer the question.

Now, if we combine the two statements, we know that Pipe A take 40 hours to fill the cistern.
Pipe B takes 120 hours to fill the cistern.

If they worked alternately, then either Pipe A could have started the cycle or Pipe B could have started the cycle.

If Pipe A started the sequence of filling alternately, then at the end of two hours, the two pipes together would have filled 1/40 + 1/120 = 1/30  th of the tank in an hour. Or the cistern will fill in 30 hours.

If Pipe B started the sequence, then at the end of 2 hours, the two pipes together would have filled 1/120 + 1/40 = 1/30 th of the tank in an hour. Or the cistern will fill in 30 hours.

As the answer obtained irrespective of which pipe started the sequence is the same, the correct answer is (3) - i.e., both the statement are sufficient to answer the question.

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Filed Under: Statement and Conclusions
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4 6374
Q:

Find the one which does not belong to that group ?

A) Architect B) Blacksmith
C) Sculpture D) Tailor
 
Answer & Explanation Answer: A) Architect

Explanation:

All except Architect are manufactures.

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Filed Under: Analogy
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5 6371
Q:

If a trader sold two cars each at Rs. 404415 and gains 15% on the first and loses 15% on the second, then his profit or loss percent on the whole is ?

A) 1.44 % B) 2.02 %
C) 1.04 % D) 2.25 %
 
Answer & Explanation Answer: D) 2.25 %

Explanation:

SP of each car is Rs. 404415, he gains 15% on first car and losses 15% on second car.

In this case, there will be loss and percentage of loss is given by = [(profit%)(loss%)]/100
= (15)(15)/100 % = 2.25%
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4 6351
Q:

At what time will B catch up with A, if A starts from a place at 11.00 A.M. and travels at a speed of 3.5 kmph, B starts at 1.00 P.M. and travels with speeds of 1 kmph for 1 hour, 2 kmph for the next 1 hour, 3 kmph for the next 1 hour and so on.

A) 8 : 47 pm B) 6 : 40 pm
C) 8 : 42 pm D) 7 : 40 pm
 
Answer & Explanation Answer: D) 7 : 40 pm

Explanation:

At 1 pm ... Distance between A and B = 2x3.5 = 7 kms
at 2 pm .....Distance between A and B = 7 + 3.5 - 1 = 9.5 kms
At 3 pm ....Distance between A and B = 9.5 + 3.5 - 2 = 11 kms.
..
..
..
At 7 pm distance between A and B = 3 kms.
From 7 pm to 8 pm, speed of A = 3.5 kmph
speed of B = 8 kmph
Relative speed = 4.5 kmph

Time taken by B to meet A = 3/4.5 hrs = 30/45 hrs = 120/3 mins = 40 mins.

So meeting time is 7 : 40 PM.

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Filed Under: Arithmetical Reasoning
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Q:

The edge of three cubes of metal is 3 m, 4 m and 5 m. They are melted and formed into a single cube. Find the edge of the new cube  ?

A) 15 m B) 4 m
C) 6 m D) 9 m
 
Answer & Explanation Answer: C) 6 m

Explanation:

The edge of the new cube is = 33+43+53 = a3 => a = 6 m.

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Filed Under: Area
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