Logical Reasoning set 9

The logical reasoning, also known as critical thinking or analytic reasoning, involves one's ability to isolate and identify the various components of any given argument.So, it is not a surprise that the logical reasoning questions commonly appear in any placement tests, competitive exams or entrance exams.

1) A man walks 30 meters towards South. Then , turning to his right, he walks 30 meters. Then turning to his left, he walks 20 meters. again he turns to his left and walks 30 meters. How far is he from his initial position?

Time:  

A) 20m

wrong answer

B) 30m

wrong answer

C) 40m

wrong answer

D) 50m

right answer

solution: D) 50m

explanation :

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2)There ia truck which should reach some place at 11'o clock , if it travels with 30 mph it reaches i hour before, if it travles with 20 mph it reaches 1 hour late. what is the distance it must be travlled and what is the speed it must maintain to rech at exact time?

Time:  

A) 120,24

right answer

B) 150,26

wrong answer

C) 120,26

wrong answer

D) 150,24

wrong answer

solution:  A) 120,24

explanation:

let T is exact time has to be taken by truck
let X is distance traveled
so
X=30(T-1)............(I)
X=20(T+1)............(II)

equating eq(I)&(II) we get
30(T-1)=20(T+1)
T=5

puting value of T in in eq(I)
X=30(5-1)
X=120miles
distance traveled = 120miles

speed=X/T;
speed=120/5
speed=24mph

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3)What number comes next in the following sequence: 2, 2, 4, 12, 48, ___ ?

Time:  

A) 256

wrong answer

B) 576

wrong answer

C) 120

wrong answer

D) 240

right answer

solution: D) 240

explanation:
a(1) = 2 * 1! = 2 * (1) = 2
a(2) = 2 * 2! = 2 * (2 * 1) = 4
a(3) = 2 * 3! = 2 * (3 * 2 * 1) = 12
a(4) = 2 * 4! = 2 * (4 * 3 * 2 * 1) = 48
so next no should be
a(5) = 2 * 5! = 2 * (5 * 4 * 3 * 2 * 1) = 240 

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4)If in coded language
23 = 10 
72 = 63 
65 = 66 
84 = 96 
Then
97 = ?

Time:  

A) 144

right answer

B) 100

wrong answer

C) 64

wrong answer

D) 169

wrong answer

solution: A) 144

explanation:

2x(2+3)=10
7x(7+2)=63
6x(6+5)=66
8x(8+4)=96
9x(9+7)=144

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5)5 cats can catch 5 mice in 5 minutes. How many cats does it take to catch 100 mice in 100 minutes?

Time:  

A) 100 cats

wrong answer

B) 5 cats

right answer

C) 20 cats

wrong answer

D) 1 cats

wrong answer

solution: B) 5 cats

explanation:

If 5 cats catch 5 rats in 5 minutes,
then 1 cat can catch 1 rat in the same 5 minutes,
or put another way, a single cat can catch 1/5 of a rat per minute.
So 1 cat can catch 100/5= 20 rats in 100 minutes,
so 5 cats can catch 100 rats in 100 minutes.

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6)Is b a positive number? (1) 1,452(b) > 0; (2) –b < 0

Time:  

A) Statement (1) ALONE is sufficient, but statement (2) is not sufficient.

wrong answer

B)  Statement (2) ALONE is sufficient, but statement (1) is not sufficient.

wrong answer

C) BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

wrong answer

D) EACH statement ALONE is sufficient.

right answer

solution:  D) EACH statement ALONE is sufficient.

explanation:

For statement(1), the fact that a positive number multiplied by b has a positive product establishes that b is a positive number.

For statement(2), any positive number with a negative sign placed in front of it will become negative, indicating that b is a positive number.

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7)Find the 8th term of this series 4,8,14,22,32 ?

Time:  

A) 74

right answer

B) 58

wrong answer

C) 24

wrong answer

D) 48

wrong answer

solution:  A) 74

explanation:

1st number is 4
2nd number is 4 +4=8
3rd number is 8 +6=14
4th number is 14+8=22
5th number is 22+10=32
6th number is 32+12=44
7th number is 44+14=58
8th number is 68+16=74

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8)2 2 12 12 30 30 -
What is the next digit.

Time:  

A) 120

wrong answer

B) 56

right answer

C) 42

wrong answer

D) 58

wrong answer

solution:  B) 56

explanation:

1^2+1=2
2^2-2=2
3^2+3=12
4^2-4=12
5^2+5=30
6^2-6=30
so next two terms are
(7^2+7)=56 

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9)If a refrigerator contains 12 cans such that 7 blue cans and 5 red cans. In how many ways can we remove 8 cans so that atleast 1 blue can and 1 red can remains in the refrigerator?

Time:  

A) 495

wrong answer

B) 455

right answer

C) 315

wrong answer

D)498

wrong answer

solution:  B) 455

explanation:

possible draw 8 cans and in refrigerator contains atleast 1 blue and 1 red cans are (6,2) (5,3) (4,4)
6 2---->7c6*5c2--->7*10=70
5 3---->7c5*5c3--->21*10=210
4 4---->7c4*5c4--->35*5=175

Total = 70+210+175=455

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10)A person travels at a speed of 10 mph from one city to another. However while returning as there was  not much traffic. He  came with a speed of 15mph. what is his average speed?

Time:  

A)12.5

wrong answer

B)12

right answer

C)11

wrong answer

D)13

wrong answer

solution:  B)12

explanation:

Don't fall in the trap of just averaging the 2 speeds.Overall average speed is not (S1+S2)/2.
Total average speed is simply = Total distance/Total time

Lets say,
D = distance travelled by the car in EACH direction
t1 = time spent on onward trip
t2 = time spent on return trip
Thus, the total distance travelled by the car = D+D= 2D
And, by the formula, Speed = Distance/Time
S1 = D/t1 => t1 = D/S1
S2 = D/t2 => t2 = D/S2
Total average speed = Total Distance/Total time = 2D/(t1+t2) = 2D/(D/S1+D/S2) = 2S1*S2/(S1+S2)

So Total average speed = 2S1*S2/(S1+S2) =2(10*15)/(10+15)=300/25=12

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