M4maths Previous Puzzles

05 Oct 2018 Age

A father said to his son, "I was as old as you are at the present at the time of your birth". If the father's age is 45 years now, what was the son's age three and half years years back?

OPtion

1) 19
2) 16
3) 18
4) 17
5) 15
6) 14
7) 13
8) 20
9) 21
10) None of these

Solution

Let the sons current age be x
So fathers age x years back when son was born => 45-x = x
Solving we get x = 22.5
3.5 Years back son's age = 22.5-3.5 = 19 years

Option 1)

Correct Option: 1 Best Solution (7)

04 Oct 2018 Fraction

If a/b = 21/34, b/c = 121/120, c/d = 17/77, e/f = 11/15 and d/e = 14/17 then what is the value of (abc/def)*2 ?

OPtion

1) 100
2) 200
3) 1/3
4) 2/595
5) 110/360
6) 77/180
7) 121/360
8) 121/260
9) 19/60
10) None of these

Solution

a/d = (a/b)*(b/c)*(c/d) = 11/80
b/e = (b/c)*(c/d)*(d/e) = 11/60
c/f = (c/d)*(d/e)*(e/f) = 2/15

So 100*abc/def = 100*(a/d)*(b/e)*(c/f) = 100*(11/80) *(11/60) * (2/15) = 121/18000

Option 10)

Correct Option: 7 Best Solution (3)

03 Oct 2018 Earthquake

The tremors of earthquake are felt at interval of 25 seconds.The first tremor was felt at 02:54:57 and the last tremor was felt at 10:45:22 am. How many times were the tremors felt?

OPtion

1) 441
2) 2361
3) 1417
4) 1119
5) 2360
6) 1416
7) 1179
8) 440
9) 1219
10) None of these

Solution

The time duration of earthquake = Duration Between first and last tremor = 10:45:22 - 02:54:57

For ease of calculation, let's assume that first tremor was at 02:45:22
Number of hours between 02:45:22 and 10:45:22 = 8 Hours = 8 * 60 *60 seconds = 28800 seconds

But in reality, its less than 8 hours as tremors started at 02:54:57 instead of 02:45:22
So time duration between 02:54:57 and 02:45:22 = 9 minutes 35 seconds = 575 seconds

The total duration of the earthquake in seconds = 28800 - 575 = 28225
The tremor was felt every 25 seconds so the number of times tremor was felt in 28225 seconds = 28225/25 = 1129

1129+1 = 1130 (Note: +1 for the first tremor)

Option 10

Correct Option: 10 Best Solution (3)

02 Oct 2018 Probability

Following is one of the quotes by Mahatama Gandhi:
"Strength does not come
from physical capacity.
It comes from an indomitable will."

An alphanumeric character is randomy picked from this quote, what is the probability that it would contain one of the following letters: G or A or N or D or H or I?
Note: Alphanumeric character means alphabet or number. Space and other characters should be ignored.

OPtion

1) 1/3
2) 10/33
3) 19/67
4) 7/22
5) 3/11
6) 20/67
7) 3/10
8) 18/67
9) 19/66
10) None of these

Solution

Count of total letters = 67
Count of G's = 1
Count of A's = 5
Count of N's = 4
Count of D's = 2
Count of H's = 2
Count of I's = 6

Total count of positive outcomes = 20

Probability = 20/67

Option 6)

Correct Option: 6 Best Solution (2)

01 Oct 2018 Profit and Loss

"A shopkeeper sells his goods at cost price but uses a weight of
890 gm instead of kilogram weight. What is his profit percentage?"

OPtion

1) 12.04
2) 12.036
3) 13.36
4) 12.36
5) 21.36
6) 12.63
7) 17.86
8) 11.12
9) 14.02
10) None of these

Solution

Let the CP of 1000 gm (1 kg) be Rs. 1000
Then CP of 890 gm = Rs 890
SP of 890gm = Rs 100

Profit = (1000-890)*100/890 = (110/890)*100 = 12.36
Option 4)

Correct Option: 4 Best Solution (6)

28 Sep 2018 Profit and Loss

250 Mangoes are bought for Rs. 4500 and sold at the rate of Rs. 250 per dozen. The percentage of profit or loss is:

OPtion

1) 15.55 % Profit
2) 15.16 % Loss
3) 16.41 % Profit
4) 15.74 % Profit
5) 16.667 % Profit
6) 16.14 % Profit
7) 18.00 % Profit
8) 16.67 % Profit
9) 15.5 % Profit
10) None of these

Solution

Cost of 1 Mango = 4500/250 = 18
Selling price of 1 Mango = 250/12 = Rs. 20.8333

As SP > CP so its profit
So Profit % = (20.8333- 18 )*100/18 = 15.74074 = ~15.74 %

Option 4)

Correct Option: 4 Best Solution (0)

27 Sep 2018 Bankers Discount

The banker's discount on a bill due 6 months hence at 9% is Rs. 5700. What is the true discount?

OPtion

1) 5401.66
2) 5404.96
3) 5494.54
4) 5445.65
5) 5418.88
6) 5429.41
7) 5478.88
8) 5407.23
9) 5411.26
10) None of these

Solution

T.D.=B.D. x 100 /(100 + (R x T))
=> 5700*100/(100+(9*6/12))
=> ~5454.54

Option 10)

Correct Option: 10 Best Solution (3)

26 Sep 2018 Probability

If two letters are taken at random from the word DREAM, what is the probability that none of the letters would be vowels?

OPtion

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

Solution

P(first letter is not vowel) = 3/5

P(second letter is not vowel) = 2/4 = 1/2

So, probability that none of letters would be vowels is = (3/5)×(1/2)=3/10

Correct Option: 7 Best Solution (7)

25 Sep 2018 Series

10321920, 645120, 46080, 3840, ...
Find the sixth term of following series

OPtion

1) 372
2) 350
3) 300
4) 384
5) 396
6) 40
7) 64
8) 48
9) 42
10) None of these

Solution

Terms are continuously divided by 16, 14, 12, 10, 8 and so on
Series is 10321920, 645120, 46080, 3840, 384, 48...

Option 8)

Correct Option: 8 Best Solution (0)

24 Sep 2018 Simple Interest

At what simple interest rate percent per annum will a sum of money double in 12 years.

OPtion

1) 7.50
2) 8.00
3) 8.33
4) 8.50
5) 7.25
6) 8.18
7) 8.75
8) 7.75
9) 8.66
10) None of these

Solution

SI = PRT/100

SI = P

So P = P*R*12/100
= R= 100/12 = 8.33
Option 3)

Correct Option: 3 Best Solution (0)