GATE Questions and Answers with Explanation

Q:

From a container of wine, a thief has stolen 15 litres of wine and replaced it with same quantity of water. He again repeated the same process. Thus, in three attempts the ratio of wine and water became 343 : 169. The initial amount of wine in the container was:

A) 75 litres	B) 100 litres
C) 150 litres	D) 120 litres

Answer & Explanation Answer: D) 120 litres

Explanation:

$\frac{w i n e (l e f t)}{w i n e (a d d e d)} = \frac{343}{169}$

It means $\frac{w i n e (l e f t)}{w i n e (i n i t i a l a m o u n t)} = \frac{343}{512}$ (since 343 + 169 = 512)

Thus, $343 x = 512 x {(1 - \frac{15}{k})}^{3}$

$\frac{343}{512} = {(\frac{7}{8})}^{3} = {(1 - \frac{15}{k})}^{3}$

$(1 - \frac{15}{k}) = \frac{7}{8} = (1 - \frac{1}{8})$

Thus the initial amount of wine was 120 liters.

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29 8154

Q:

The average age of 7 boys is increased by 1 year when one of tem whose age is replaced by a girl. What is the age of the girl ?

A) 33 yrs	B) 27 yrs
C) 21 yrs	D) 29 yrs

Answer & Explanation Answer: D) 29 yrs

Explanation:

Let the avg age of 7 boys be 'p' years
Let the age of the girl be 'q' years
From given data,
The age of 7 boys = 7p years
Now the new average = (p + 1) when 22 yrs is replaced by q
Now the age of all 7 will become = 7(p + 1) yrs
Hence, 7p - 22 + q = 7(p + 1) yrs
7p - 22 + q = 7p + 7
q = 22 + 7 = 29

Therefore, the age of girl = q = 29 years.

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17 8145

Q:

20 men went to a restaurant. Ninteen of them paid Rs.70 each and the twentieth man paid Rs.90.25 more than the average of all the 20 men. What is the total bill ?

A) Rs. 1495	B) Rs. 548
C) Rs. 850	D) Rs. 1750

Answer & Explanation Answer: A) Rs. 1495

Explanation:

Let the average bill paid by twenty members = 'x'

But 19 men paid each = Rs. 70

20th man paid Rs. 90.25 more than the avg bill of 20 = x + 90.25

20x = 19(70) + x + 90.25
19x = 1330 + 90.25
19x = 1420.25
x = 1420.25/19 = Rs. 74.75

But the total bill = 20 x 74.75 = Rs. 1495.

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10 8144

Q:

Two boys are playing on a ground. Both the boys are less than 10 years old. Age of the younger boy is equal to the cube root of the product of the age of the two boys. If we place the digit representing the age of the younger boy to the left of the digit representing the age of the elder boy, we get the age of the father of the younger boy. Similarly, we place the digit representing the age of the elder boy to the left of the digit representing the age of the younger boy and divide the figure by 2, we get the age of the mother of the younger boy. The mother of the younger boy is younger than his father by 3 years. Then, what are the ages of elder and younger boys ?

A) E = 15 & Y = 3	B) E = 14 & Y = 12
C) E = 40 & Y = 22	D) E = 4 & Y = 2

Answer & Explanation Answer: D) E = 4 & Y = 2

Explanation:

Let the the age of the elder boy = E

Let the the age of the younger boy = Y

Given that Y = cube root of EY

=> $Y^{3}$ = EY => E = $Y^{2}$ .....(1)
By the condition of number replacement the age of the father is YE

The Mother's age = EY/2

But she is 3 years less than father => EY/2 + 3 = YE
2YE = EY + 6 ......(2)

Then now from the given options we can identify which satisfies the all the conditions.

Here Y =2 and E = 4 satisfies all the conditions.

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8 8143

Q:

Solve the Missing Number Puzzle ?

missing_number1501485405.jpg image

Answer

The rule followed here is

7 + 3 - 4 = 6

Similarly,

4 + 2 - 2 = 4

9 + 5 - 4 = 10

Hence, the missing numbers are 4 & 10.

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Subject: Number Puzzles Exam Prep: GATE , CAT , Bank Exams , AIEEE
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41 8136

Q:

One-third of the boys and one-half of the girls of a college participated in a sport. If the number of participating students is 300, out of which 100 are boys. What is the total number of students in the college?

A) 500	B) 300
C) 600	D) 700

Answer & Explanation Answer: D) 700

Explanation:

Let number of boys in the school = x

Let number of girls in the school = y

Number of students participated in the sports = 300

Out of which boys = 100

but given number of boys participated in sports = x/3

=> x/3 = 100

=> x = 300

Remaining girls = 300 - 100 = 200

=> y/2 = 200

=> y = 400

Therefore, total number of students in the school = x + y = 300 + 400 = 700

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15 8120

Q:

If N is the greatest number that will divide 1305, 4665 and 6905, leaving the same remainder in each case. What is the sum of the digits of N ?

A) 6	B) 8
C) 4	D) 9

Answer & Explanation Answer: C) 4

Explanation:

N = H.C.F. of (4665 - 1305), (6905 - 4665) and (6905 - 1305)

= H.C.F. of 3360, 2240 and 5600 = 1120.

Sum of digits in N = ( 1 + 1 + 2 + 0 ) = 4

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17 8119

Q:

1001 A N means

Answer

1001 A N means 1001 Arabian Nights.

These are same as 12 S of the Z, 64 S on a C, 19 C in CB, 8 S on SS, ...

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7 8110

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