GATE Questions and Answers with Explanation

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 = $\frac{100}{100 + P} \times S P$ = 5000/6 = 2500/3

SP of second article = 1000

Loss = 20%

CP = $\frac{100}{100 - L} \times S P$ = 5000/4 = 1250

Total SP = 2000

Total CP = $\frac{2500}{3}$ + 1250 = 6250/3

CP is more than SP, he makes a loss.

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

Loss Percent = $\frac{\frac{250}{3}}{\frac{6250}{3}} \times 100$ = 4%

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Filed Under: Profit and Loss
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5 5676

Q:

Nine different letters of alphabet are given, words with 5 letters are formed from these given letters. Then, how many such words can be formed which have at least one letter repeated ?

A) 43929	B) 59049
C) 15120	D) 0

Answer & Explanation Answer: A) 43929

Explanation:

Number of words with 5 letters from given 9 alphabets formed = $9^{5}$

Number of words with 5 letters from given 9 alphabets formed such that no letter is repeated is = $9 P_{5}$

Number of words can be formed which have at least one letter repeated = $9^{5} - 9 P_{5}$

= 59049 - 15120

= 43929

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Filed Under: Permutations and Combinations
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11 5657

Q:

A room contains 3 brown, 5 black and 4 white chairs. Two chairs are picked and are put in the lawn. What is the probability that none of the chairs picked is white ?

A) 14/33	B) 14/55
C) 12/55	D) 13/33

Answer & Explanation Answer: A) 14/33

Explanation:

Total number of chairs = (3 + 5 + 4) = 12.

Let S be the sample space.

Then, n(s)= Number of ways of picking 2 chairs out of 12

$=^{12} 12_{2} = \frac{12 \times 11}{2 \times 1} = 66$

Let n(E) = number of events of selecting 2 chairs for selecting no white chairs.

$=^{8} C_{2} = \frac{8 \times 7}{2 \times 1} = 28$

Therefore required probability = 28/66 = 14/33.

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Filed Under: Probability
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15 5649

Q:

A tank is filled in eight hours by three pipes K, L and M. Pipe K is twice as fast as pipe L, and L is twice as fast as M. How much time will pipe L alone take to fill the tank ?

A) 32 hrs	B) 24 hrs
C) 28 hrs	D) 26 hrs

Answer & Explanation Answer: C) 28 hrs

Explanation:

1/K + 1/L + 1/M = 1/8 (Given)
Also given that K = 2L and L = 2M
=> 1/2L + 1/L + 2/L = 1/8
=> (1 + 2 + 4)/2L = 1/8
=> 2L/7 = 8
=> L = 28 hours.

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Filed Under: Pipes and Cistern
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8 5639

Q:

What is the oxidation number of carbon in NaHCO3?

A) -4	B) -3
C) +4	D) +2

Answer & Explanation Answer: C) +4

Explanation:

The given compound is NaHCO3 Sodium bicarbonate which is commonly known as Baking soda.

Oxidation numbers are the charges on ions. When a neutral atom loses electrons it becomes positively charged. When a neutral atom gains electrons it becomes negatively charged.

Here the C represents the oxidation state of carbon in this compound. Compounds are electrically neutral, which is why we set the sum of the oxidation states equal to zero.

Sodium has a +1 oxidation state. Hydrogen has a +1 oxidation state. Oxygen has a -2 oxidation state. There are three oxygen atoms, which means the total oxidation state provided by both oxygen ions is -6. Adding up these oxidation states we get:

1 + 1 + (-6) + C = 0

-4 + C = 0

=> C = 4

This means the oxidation state of carbon in this compound is +4.

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Filed Under: Chemistry
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1 5636

Q:

In how many ways the letters of the word NUMERICAL can be arranged so that the consonants always occupy the even places ?

A) 5!	B) 6!
C) 4!	D) Can't determine

Answer & Explanation Answer: D) Can't determine

Explanation:

NUMERICAL has 9 positions in which 2, 4, 6, 8 are even positions.

And it contains 5 consonents i.e, N, M, R, C & L. Hence this cannot be done as 5 letters cannot be placed in 4 positions.

Therefore, Can't be determined.

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Filed Under: Permutations and Combinations
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6 5623

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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17 5616

Q:

Prasanna invested certain amount in three different schemes X, Y and Z with the rate of interest 10% p.a, 12% p.a and 15% p.a respectively. If the total interest accrued in one year was Rs. 3200 and the amount invested in Scheme Z was 150% of the amount invested in Scheme X and 240% of the amount invested in Scheme Y, what was the amount invested in Scheme Y by Prasanna ?

A) Rs.6000	B) Rs.4500
C) Rs.7500	D) Rs.5000

Answer & Explanation Answer: D) Rs.5000

Explanation:

Let a, b and c be the amounts invested in schemes X, Y and Z respectively. Then,

As we know:

Simple interest (S.I.) = PTR/100

(a × 10 × 1/100) + (b × 12 × 1/100) + (c × 15 × 1/100) = 3200

= 10a + 12b + 15c = 320000 .........(1)

Now, c = 240% of b = 12b/5 .........(2)

And, c = 150% of a = 3a/2 => a = 2/3 c = (2 × 12)b/(3 × 5) = 8b/5 .......(3)

From (1), (2) and (3), we have

16b + 12b + 36b = 320000 => 64b = 320000 => b = 5000

∴ Sum invested in Scheme Y = Rs.5000.

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Filed Under: Percentage
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9 5608

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