M4maths Previous Puzzles

20 Dec 2019 LCM

What is the least number which when doubled will be exactly divisible by 12, 16, 22 and 26 ?

OPtion

1) 6864
2) 6868
3) 6860
4) 13728
5) 13724
6) 13720
7) 3430
8) 3432
9) 3434
10) None of these

Solution

LCM of 12, 16, 22 and 26 = 6864

Hence the least number which will be exactly divisible by 12, 16, 22 and 26 = 6864

6864 ÷ 2 = 3432

Correct Option: 8 Best Solution (3)

19 Dec 2019 Logarithm

Find the logarithm of 144 to the base 2√3 ?
(note: 2√3 = two root three)

OPtion

1) 5
2) 6
3) 7
4) 8
5) 4
6) 2√3
7) 4√3
8) 8√3
9) 10√3
10) None of these

Solution

144 = 12 x 12 = 4 x 3 x 4 x 3 = 2^4 x 3^2 = 2^4 x √3^4 = (2√3)^4

Logarithm 144 to the base 2√3 = Logarithm (2√3)^4 to the base 2√3
=> 4

Correct Option: 5 Best Solution (8)

18 Dec 2019 Probability

In a zoo, there are 15 rabbits and 10 rhinos. Three animal are selected at random. The probability that 1 rhino and 2 rabbits are selected, is:

OPtion

1) 1025/2300
2) 1040/2300
3) 1050/2200
4) 1060/2300
5) 1075/2300
6) 19/45
7) 21/46
8) 22/45
9) 23/46
10) None of these

Solution

Number ways of selecting 3 animal out of 25 = 25C3 = 2300
Number of ways that 1 rhino and 2 rabbits are selected = 10C1×15C2 = 1050

P(E) = 1050/2300 = 21/46

Correct Option: 7 Best Solution (6)

17 Dec 2019 Speed

Kaju and Raju start running from the same place at a rate of 7.6 kmph and 7.85 kmph respectively. What time in hours will they take to be 13.5km apart, if they walk in the same direction?

OPtion

1) 50
2) 51
3) 52
4) 53
5) 54
6) 55
7) 56
8) 57
9) 58
10) None of these

Solution

The relative speed of the boys = 7.85kmph – 7.6kmph
= 0.25 kmph

3Distance between them is 13.5 km
Time = Distance/Speed
Time= 13.5km / 0.25 kmph = 54 hrs

Correct Option: 5 Best Solution (1)

16 Dec 2019 Average

Average of six numbers is 47. If each number is multiplied by 2, what will be the new average?

OPtion

1) 141
2) 140
3) 142
4) 188
5) 189
6) 84
7) 87
8) 94
9) 97
10) None of these

Solution

The new average = Initial average ∗ 2

= 47∗ 2 = 94

Correct Option: 8 Best Solution (0)

13 Dec 2019 Profit & Loss

Mallya bought a mobile from a shop. If he sells it at Rs. 18400 to Mukesh and earns a profit of 28%, find the price at which Mallya bought the mobile.

OPtion

1) 17375
2) 16375
3) 15375
4) 14315
5) 13375
6) 14375
7) 12375
8) 11375
9) 18375
10) None of these

Solution

CP = (18400)*100/128 = 14375

Correct Option: 6 Best Solution (4)

12 Dec 2019 Average

What is the average of all multiples of 12 lying between
424 and 530

OPtion

1) 476
2) 472
3) 470
4) 480
5) 468
6) 466
7) 464
8) 462
9) 478
10) None of these

Solution

432
444
456
468
480
492
504
516
528
Average = 4320/9 = 480

Correct Option: 4 Best Solution (7)

11 Dec 2019 Area

The ratio of length and breadth of a rectangular park is 6:3. If a squirrel running along the boundary of the park at the speed of 24 km/hr completes one round in 12 minutes, find the area of the park in square meters.

OPtion

1) 1260000
2) 1270000
3) 1280800
4) 1290000
5) 1200000
6) 1210000
7) 1280000
8) 1230000
9) 1208000
10) None of these

Solution

One round of the park is equal to the perimeter of the park.

So, by completing one round, the squirrel covers a distance equal to the perimeter of the park.

Now, Distance or perimeter = speed * time
= 24 * (12/60)
= 4.8 km or 4800 meters

Let Length = 6x and breadth = 3x

So, Perimeter: 2 (6x + 3x) = 4800
18x = 4800

x= 4800/18

So, Length = 6*(4800/18) = 1600 meters

And, Breadth = 3*(4800/18) = 800 meters

Area = Length * Breadth
= 1600 * 800
= 1280000 sq. m.

Correct Option: 7 Best Solution (1)

10 Dec 2019 Age

The present ages of A,B and C are in proportions 3:6:8. Five years ago, the sum of their ages was 70. What is the product of their present ages?

OPtion

1) 7500
2) 12960
3) 3840
4) 12096
5) 18000
6) 24000
7) 43740
8) 42000
9) 19440
10) None of these

Solution

Answer: 18000 years

Five years ago sum of Ages of A, B and C = 70
Five years later i.e. sum of current ages of A, B and C =
70 + 3*5 = 85

Present Age of A = 85*3/(3+6+8) = 15 years

Present Age of B = 85*6/(3+6+8) = 30 years
Present Age of C = 85*8/(3+6+8) = 40 years

Product of their ages = 18000

Option 4)

Correct Option: 5 Best Solution (4)

09 Dec 2019 Probability

The tickets numbered from 99 to 116 are mixed up and then a ticket is drawn at random. What is the probability that the ticket has a number which is a multiple of 3 or 5?

OPtion

1) 7/16
2) 9/16
3) 7/17
4) 8/17
5) 9/17
6) 10/17
7) 1/2
8) 8/18
9) 7/18
10) None of these

Solution

Multiple of 3: 99, 102, 105, 108, 111, 114
Count = 6
Multiples of 5 which are not multiples of 3 = 100, 110, 115
Count = 3
Total = 6+3 = 9

Total numbers between 99 and 116 = 18

Probability = 9/18 = 1/2

Correct Option: 7 Best Solution (1)