M4maths Previous Puzzles

13 Mar 2020 Logarithm

What is the value of
2*log 5 + log 8 – (1/2)*log 4 = ?
Assumed all Logs are of base 10

OPtion

1) 1
2) 0
3) 10
4) 100
5) 2
6) 20
7) 10^(1/2)
8) 18
9) 24
10) None of these

Solution

2 log 5 + log 8 – ½ log 4

= log (5^2) + log 8 - log (4^(1/2))

= log 25 + log 8 - log 2 = log (25*8)/2

= log 100 =log 10^2 = 2 log 10 = 2 * 1 =2

Correct Option: 5 Best Solution (2)

12 Mar 2020 Chain

A certain number of workers can finish a piece of work in 100 days. If there were 10 workers less, it would take 10 days more for the work to be finished. How many workers were there originally?

OPtion

1) 90
2) 95
3) 100
4) 105
5) 110
6) 115
7) 120
8) 125
9) 130
10) None of these

Solution

Let there be x workers initially.

Less men, More days
(x-10) : x :: 100 :110

=> (x - 10) * 110 = x * 100 => x= 110

Correct Option: 5 Best Solution (0)

11 Mar 2020 Boats and Streams

A man can row a boat at 25/9 meters per second in still water and the speed of the stream is 8 kmph. What is the
time taken (in hours) to row a distance of 90 km down the stream ?

OPtion

1) 20
2) 5
3) 15
4) 16
5) 25
6) 6
7) 8
8) 7
9) 10
10) None of these

Solution

Speed in down stream = 10 +8 = 18

Time taken to cover 90 km down stream = 90/18 = 5 hrs.

Correct Option: 2 Best Solution (3)

10 Mar 2020 CODE DECODE

If
GOLI = 11383
ROLI = 29214

then HOLI =?

OPtion

1) 12960
2) 13004
3) 12619
4) 12679
5) 13678
6) 13879
7) 12579
8) 13379
9) 12179
10) None of these

Solution

A= 1, B=2. C=3. D=4....Z=26

Each word is coded as = Sum of P and S = P+S

Where P = Product of each alphabets position value
and S= Sum of each alphabets position value

So For HOLI
=(8*15*12*9)+(8+15+12+9) = 13004

Correct Option: 2 Best Solution (3)

09 Mar 2020 Simple Interest

A sum amounts to Rs 2565.4
at the rate of 9 %.p.a. in 3 years. What is the sum?

OPtion

1) 9501.48
2) 1940.00
3) 1980.00
4) 1960.00
5) 2010.00
6) 2002.00
7) 2020.00
8) 2030.00
9) 2060.00
10) None of these

Solution

A = P (1+ RT/100 )
2565.4 = A (1 + 3*9/100)
=> 2565.4 = A (127/100)
=> 2020

Correct Option: 7 Best Solution (4)

06 Mar 2020 Arithmatic

If x is the average (arithmetic mean) of 4a and 26, y is the average of 5a and 36, and z is the average of 3a and 28, what is the average of x , y, and z in terms of a?

OPtion

1) a+5
2) 2a+5
3) a+10
4) a+15
5) 3a+5
6) 3a+10
7) 2a+15
8) 4a+5
9) 4a+!5
10) None of these

Solution

Since the average (arithmetic mean) of two numbers is equal to the sum of the two numbers divided by 2, the equations x= (4a+26)/2
y = (5a+36)/2 and
z = (3a+28)/2


The average of x, y, and z is given by (x+y+z)/3

Substituting the expressions in a for each variable (x, y, z) gives = ((4a+26)/2 + (5a+36)/2 + (3a+28)/2)/3 = (12a+90)/6 = 2a + 15

Correct Option: 7 Best Solution (2)

05 Mar 2020 LCM

What is the LCM of 18, 24, 9, 36 and 90?

OPtion

1) 360
2) 320
3) 225
4) 290
5) 335
6) 315
7) 340
8) 375
9) 350
10) None of these

Solution

Least common multiple (L.C.M) of 18, 24, 9, 36 and 90 = 2 × 2 × 3 × 3 × 2 × 5 = 360

Correct Option: 1 Best Solution (1)

04 Mar 2020 Probability

Out of 12 months of the years, a month is randomly picked what is the probability that its name starts with "J" followed by a vowel?

OPtion

1) 1/12
2) 2/3
3) 2/5
4) 1/6
5) 1/2
6) 1/4
7) 2/7
8) 3/7
9) 5/12
10) None of these

Solution

Count of months whose name starts with a J = Jan, Jun and Jul => 3

Required probability = 3/12 = 1/4

Correct Option: 6 Best Solution (3)

03 Mar 2020 Arithmetic

The sum of squares of three successive integers is 26510. Sum of these integers is?

OPtion

1) 221
2) 282
3) 223
4) 281
5) 224
6) 286
7) 288
8) 226
9) 228
10) None of these

Solution

(a-1)^2 + a^2 + (a+1)^2 = 26510
=> a^2 -2a + 1 + a^2 + a^2 + 2a + 1 = 26510
=> 3a^2 + 2 = 26510
=> a^2 = (20174-2)/3 = 8836
=> a = 94
So the 3 numbers are 93, 94 and 95 and their sum is 282

Correct Option: 2 Best Solution (3)

02 Mar 2020 Simple Interest

How much time will take for an amount of Rs. 900 to yield Rs. 162 as interest at 9% per annum of simple interest ?

OPtion

1) 1 years
2) 1.5 years
3) 2.0 years
4) 2.5 years
5) 3.0 years
6) 3.5 years
7) 4.0 years
8) 2.25 years
9) 4.5 years
10) None of these

Solution

Time = (100 x 162) / (900 x 9) = 2 years.

Correct Option: 3 Best Solution (5)