Question Bank  100 Arithmetic Questions From Previous CAT Papers (Solved)

Both trip took the same time.
Same route so same distance.
a. False, as average speed is same.
b. We cannot say that as we don't know if the speed is uniform or not.
c and d are conflicting statement so only one can be true.
starting point and end point are at the same time (6 am and 6 pm respectively) so c can be correct.

Q38. (CAT 1998)
There are two containers: the first contains 500 ml of alcohol, while the second contains 500 ml of water. Three cups of alcohol from the first container is taken out and is mixed well in the second container. Then three cups of this mixture is taken out and is mixed in the first container. Let A denote the proportion of water in the first container and B denote the proportion of alcohol in the second container. Then
a. A > B
b. A < B
c. A = B
d. Cannot be determined

Let's assume that volume of cup is 10 ml.
Container 1 Container 2 Water Alcohol Water Alcohol Start 0 500 500 0 Step 1 0 470 500 30 Step 2 28.3 471.7 471.7 28.3 So A = B ( did the calculations in hurry  hope it's correct!)

Q39. (CAT 1999)
The speed of a railway engine is 42 kmph when no compartment is attached, and the reduction in speed is directly proportional to the square root of the number of compartments attached. If the speed of the train carried by this engine is 24 kmph when 9 compartments are attached, the maximum number of compartments that can be carried by the engine is
a. 49
b. 48
c. 46
d. 47

Speed when no compartments attached = 42
Speed with 9 compartments attached = 24
Reduced speed = 18
18 = k * sqrt(9)
k = 6
Train doesn't move when there are more compartments. so assuming that the speed is reduced by 42
42 = 6 * sqrt(n)
n = 49
For 49 compartments, Engine won't move. So the maximum possible number of compartments = 49  1 = 48
(And no surprise we have 49 also in the option!)

Q40. (CAT 1999)
Total expenses of a boarding house are partly fixed and partly varying linearly with the number of boarders. The average expense per boarder is Rs. 700 when there are 25 boarders and Rs. 600 when there are 50 boarders. What is the average expense per boarder when there are 100 boarders?
a. 550
b. 580
c. 540
d. 570

Let the fixed amount be F and the partly varying amount be p.
F + 25p = 700 * 25
F + 50p = 600 * 50
On solving these equations we get p = 500 and F = 5000
So, for 100 people, we get 5000 + 100(500) = 55000
Hence, average expense = 55000/100 = 550.

Q41. (CAT 1997)
A thief, after committing the burglary, started fleeing at 12 noon, at a speed of 60 km/hr. He was then chased by a policeman X. X started the chase, 15 min after the thief had started, at a speed of 65 km/hr.At what time did X catch the thief?
a. 3.30 p.m.
b. 3 p.m.
c. 3.15 p.m.
d. None of theseIf another policeman had started the same chase along with X, but at a speed of 60 km/hr, then how far behind was he when X caught the thief?
a. 18.75 km
b. 15 km
c. 21 km
d. 37.5 km

Part 1 : In the 15 minutes, thief gets a head start of 15 km.
Every hour Police man gains 65  60 = 5 km
So to cover 15 km, Police man needs 15/5 = 3 hours.
So Thief will be caught at 12.15 + 3 = 3.15 PMPart 2: Thief's speed is same as of second police man and Thief already has a 15 km head start. So this distance won't change between them.

Q42. (CAT 1997)
After allowing a discount of 11.11%, a trader still makes a gain of 14.28%. At how many percentage above the cost price does he mark on his goods?
a. 28.56%
b. 35%
c. 22.22%
d. None of these

Let the cost price be 100
SP = 114.28
114.28 = MP * (100  11.11)/100
MP = 114.28 x 100 / (100  11.11) = 128.56
which is 28.56% more than the cost price.

Q43. (CAT 1997)
A dealer buys dry fruits at Rs. 100, Rs. 80 and Rs. 60 per kilogram. He mixes them in the ratio 3 : 4 : 5 by weight, and sells at a profit of 50%. At what price per kilogram does he sell the dry fruit?
a. Rs. 80
b. Rs. 100
c. Rs. 95
d. None of these

cost price = 300 + 320 + 300 = 920 for 12 kg
profit = 460
SP = 920 + 460 = 1380
price per kg = 1380/12 = 115 ( None of the above)

Q44. (CAT 1997)
An express train travelling at 80 km/hr overtakes a goods train, twice as long and going at 40 km/hr on a parallel track, in 54 s. How long will the express train take to cross a platform of 400 m long?
a. 36 s
b. 45 s
c. 27 s
d. None of these

Let's take train length be d.
distance covered = d + 2d
relative velocity = 80  40 = 40 kmph = 40 x 5/18 ( 1 km/h = 5/18 m/s)
3d = 40 x 5/18 x 54 = 600
d = 600/3 = 200
To cross 400 m platform  total length covered = platform length + train length = 400 + 200 = 600
600 = t x 80 x 5/18
t = 600 x 18 / ( 5 x 80 ) = 27 seconds.

Q45. (CAT 1997)
The average marks of a student in 10 papers are 80. If the highest and the lowest scores are not considered, the average is 81. If his highest score is 92, find the lowest.
a. 55
b. 60
c. 62
d. Cannot be determined

Total marks = 10 x 80 = 800
Excluding highest and lowest, total marks = 648
sum of highest and lowest = 800  648 = 152
lowest = 152  92 = 60

Q46. (CAT 1997)
A man earns x% on the first Rs. 2,000 and y% on the rest of his income. If he earns Rs. 700 from income of Rs. 4,000 and Rs. 900 from if his income is Rs. 5,000, find x%.
a. 20%
b. 15%
c. 25%
d. None of these

for 4000, 2000x/100 + 2000y/100 = 700
for 5000, 2000x/100 + 1000y/100 = 900
10y = 200, y = 20
x = 15

Q47. (CAT 2002)
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 father of the younger boy. Similarly, if 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 mother of the younger boy. The mother of the younger boy is younger to his father by 3 years. Then, what is the age of the younger boy?
a. 3
b. 4
c. 2
d. None of these