M4maths Previous Puzzles

20 Sep 2019 Series

Find the twelfth term of below series is:
-1, 7, 5, 21, 19, 43, 41, .....

OPtion

1) 167
2) 169
3) 171
4) 121
5) 109
6) 177
7) 157
8) 110
9) 144
10)None of these

Solution

1^2 - 2 = -1
2^2 + 3 = 7
3^2 - 4 = 5
4^2 + 5 = 21
5^2 - 6 = 19
6^2 + 7 = 43
7^2 - 8 = 41
8^2 + 9 = 73
9^2 - 10 = 71
10^2 + 11 = 111
11^2 - 12 = 109
12^2 + 13 = 157

Correct Option: 7 Best Solution (4)

19 Sep 2019 Logarithm

If log2 + log(3x+1) = log(2x-9) + 2, then value of x is ?
Note: Assume all log represented above is to the base of 10.

OPtion

1) 441/94
2) 451/94
3) 461/94
4) 441/97
5) 461/97
6) 451/97
7) 431/97
8) 451/91
9) 451/93
10)None of these

Solution

Considering base is 10, so 1 could be represented as Log10
=> log2 + log(3x+1) = log(2x-9) + log100

Let’s revise the formula for Logs
Log(XY) = LogX+LogY
Applying the formula we get:
Log[2*(3x+1)] = Log[100*(2x-9)]
Solving
=> 6x + 2 = 200x - 900
=> 194x= 902
=> x = 451/97

Correct Option: 6 Best Solution (1)

18 Sep 2019 Mode

Find the mode of following list of values:
86 69 77
68 85 97
85 68
96 83 69 68

OPtion

1) 69
2) 97
3) 77
4) 68
5) 85
6) 86
7) 85
8) 83
9) 96
10) None of these

Solution

Mode = Number which is present maximum number of times = 68

Correct Option: 4 Best Solution (0)

17 Sep 2019 Volume

44 cubic centimeters of silver is drawn into a wire 4 mm in diameter. The length if the wire in meters will be:

OPtion

1) 3.5cm
2) 35cm
3) 35cm
4) 3500m
5) 35000cm
6) 3.5m
7) 0.35m
8) 35m
9) 350m
10) None of these

Solution

Let the length of the wire be h
Radius=4/2 mm = 1/5 cm
Volume = πr^2h= 44
=> (22/7)∗(1/5)∗(1/5)∗h = 44
=>h = (44∗5∗5∗7)/22 = 350cm = 3.5m

Correct Option: 6 Best Solution (0)

16 Sep 2019 Interest

At what rate of compound interest per annum will a sum of Rs. 5000 become Rs. 10068 in 10 years?

OPtion

1) 6.5%
2) 7.5%
3) 7.75%
4) 8.5%
5) 7.25%
6) 7.0%
7) 8.0%
8) 6.75%
9) 8.25%
10) None of these

Solution

A = P (1 + r/n)^t 
Solving for R, we get R= 7.25%

Correct Option: 5 Best Solution (1)

13 Sep 2019 LCM

Two numbers are in the ratio 7 : 11. If their L.C.M. is 308. what is sum of the numbers?

OPtion

1) 110
2) 78
3) 66
4) 64
5) 63
6) 68
7) 72
8) 60
9) 82
10) None of these

Solution

"Let the numbers be 7x and 11x
LCM of 7x and 11x is 77x

So as per question 77x = 308
=> x= 4

7x = 7*4 = 28 and 11x = 11*4 = 44

Sum of the numbers = 28+44 = 72

Correct Option: 7 Best Solution (3)

12 Sep 2019 Mixture

A mixture contains sugar solution and colored water in the ratio 5 : 8. If 22 liters of colored water is added to the mixture, the ratio becomes 3 : 7. Find the initial quantity of sugar solution in the given mixture (in liters).

OPtion

1) 20
2) 24
3) 15
4) 16
5) 30
6) 45
7) 32
8) 25
9) 36
10) None of these

Solution

The initial ratio is 5 : 8.
Let ‘k’ be the common ratio.
=> Initial quantity of sugar solution = 5 k
=> Initial quantity of colored water = 8 k
=> Final quantity of sugar solution = 5 k
=> Final quantity of colored water = 8 k + 22
Final ratio = 5 k : 8 k + 22 = 3 : 7
=> k = 6
Therefore, initial quantity of sugar solution in the given mixture (in liters) = 5 k = 30 liter

Correct Option: 5 Best Solution (0)

11 Sep 2019 Age

The present ages of A,B and C are in proportions 2:4:7. Four years ago, the sum of their ages was 66. What is the product of their present ages?

OPtion

1) 7500
2) 12960
3) 3840
4) 12096
5) 30720
6) 24000
7) 43740
8) 42000
9) 19440
10) None of these

Solution

Answer: 12096 years


Four years ago sum of Ages of A, B and C = 66
Four years later i.e. sum of current ages of A, B and C = 66 + 3*4 = 78

Present Age of A = 78*2/(2+4+7) = 12 years

Present Age of B = 78*4/(2+4+7) = 24 years
Present Age of C = 78*7/(2+4+7) = 42 years

Product of their ages = 12096

Option 4)

Correct Option: 4 Best Solution (5)

10 Sep 2019 Simplification

There are two buildings P and Q. If 35 persons are sent from P to Q, then the number of persons in each building is the same. If 60 persons are sent from Q to P, then the number of persons in P is double the number of persons in Q. How many persons are there in building P?

OPtion

1) 250
2) 320
3) 325
4) 290
5) 335
6) 315
7) 340
8) 365
9) 350
10) None of these

Solution

Let number of persons in building P be P and
number of persons in building Q be Q

P-35 = Q+35
=> P = Q + 70 ---- (i)

P+60= 2(Q-60)
=> P + 180 = 2Q ---- (ii)

Putting value of P from (i) in (ii)
Q+ 70 + 180 = 2Q
Q = 250
P = 320

Correct Option: 2 Best Solution (3)

09 Sep 2019 Simple Interest

At what simple interest rate percent per annum will a sum of money triple in 19 years.

OPtion

1) 10.50
2) 10.52
3) 9.33
4) 10.50
5) 10.53
6) 10.14
7) 10.75
8) 9.75
9) 10.66
10) None of these

Solution

SI = PRT/100

SI = 2P

So 2P = P*R*19/100
= R= 200/19 = 10.53
Option 5)

Correct Option: 5 Best Solution (0)