M4maths Previous Puzzles

11 Nov 2020 AVERAGE

The average age of a family of 18 members is 82 years. If the age of the youngest member is 12 years, the average age of the family at the birth of the youngest member was?

OPtion

1) 75
2) 70
3) 78
4) 95
5) 85
6) 72
7) 82
8) 92
9) 79
10) None of the above

Solution

Total age of the family of 18 members = 82* 18 = 1476 yrs
Total age of the family members 12 yrs ago = 1476 - (18*12) = 1260
At the time total members in a family = 18
Average age of the family at the birth of the youngest member = 1260/18 = 70yrs.

Correct Option: 2 Best Solution (3)

10 Nov 2020 sequence

0,1,-1,8,4,29,23...............
next number of the sequence will be

OPtion

1) 29
2) 34
3) 38
4) 44
5) 50
6) 63
7) 72
8) 69
9) 84
10) none of these

Solution

0+1^2 = 1
1-2 = -1
-1+3^2 = 8
8-4 = 4
4+5^2 = 29
29-6 = 23
23+7^2 = 72

Correct Option: 7 Best Solution (1)

09 Nov 2020 Drop four Letters

There are four different letters and four different letter boxes, in how many methods these letters can be dropped in the boxes,
if all the four letters in a single box are not allowed:

OPtion

1) 250
2) 248
3) 256
4) 320
5) 128
6) 252
7) 224
8) 90
9) 4
10) 16

Solution

Total no. of methods without any condition = 4*4*4*4 = 256
No of methods of taking all the four letters in a box = 4
Hence required methods with given condition = 256-4 = 252

Correct Option: 6 Best Solution (0)

05 Nov 2020 Profit & Loss

Murugan sold a book at a loss of 40%. If the selling price had been increased by Rs.200, there would have been a gain of 10%. What was the cost price of the book?

OPtion

1) 250
2) 420
3) 450
4) 500
5) 300
6) 400
7) 440
8) 380
9) 410
10) 520

Solution

Let cost price be Rs ‘x’ Then (110% of x) – (60 % of x) = 200 (110x/100) - (60x/10) = 200 110x – 60x = 20000 X = 400 So cost price of the book = Rs.400

Correct Option: 6 Best Solution (4)

04 Nov 2020 Simple interest

What amount of a man would have received on a principal amount of Rs. 4500 after two year simple interest @10% per annum?

OPtion

1) 4161
2) 5200
3) 4400
4) 4100
5) 5400
6) 5500
7) 5800
8) 5550
9) 6200
10)4850

Solution

Amount= Principal+Interest
SI= P x R x T/100
= 4500 x 10 x 2/100
= 900
Amount= 4500+900=5400

Correct Option: 5 Best Solution (4)

03 Nov 2020 TIME, SPEED AND DISTANCE

Kiran rides her scooter 14km at an average speed of 16 km/hr and again travels 16km at an average speed of 14 km/hr. What is her average speed for the entire trip approximately?

OPtion

1) 15.36 km/hr
2) 17.46 km/hr
3) 13.56 km/hr
4) 14.26 km/hr
5) 14.33 km/hr
6) 13.98 km/hr
7) 14.86 km/hr
8) 16.55 km/hr
9) 16.42 km/hr

Solution

Total distance travelled =14+16=30Km
Time taken to travel 14 km at an average speed of 16 km/hr =14/16=7/8 Hr
Time taken to travel 16 km at an average speed of 14 km/hr =16/14=8/7 hr
Total time taken =7/8+8/7 Average speed =Total distance travelled /Total time taken =30/(7/8+8/7) =30/(113/56)
=30*56/113=1680/113
=14.86 km/hr

Correct Option: 7 Best Solution (3)

02 Nov 2020 Arithmetical Progression

Find the sum of an AP of 40 terms whose first and last terms are 80 and 275.

OPtion

1) 8400
2) 7200
3) 7100
4) 4800
5) 7600
6) 8600
7) 7500
8) 6800
9) 5800
10) None of above

Solution

As given, a1= 80 and a40 = 275
S40 = n / 2 ( a1 + a40 ) = 40/2 ( 80 + 275 )
= 20 x 355 = 7100

Correct Option: 3 Best Solution (3)

30 Oct 2020 Probability

3 of our users Amar, Akbar and Anthony attempt to solve a puzzle together, their chances of solving the puzzle is 2/7, 3/5, 4/9.
What is the probability that the puzzle will be solved by them?

OPtion

1) 10/53
2) 5/33
3) 10/63
4) 53/63
5) 59/63
6) 8/105
7) 2/3
8) 53/60
9) 5/12
10) None of these

Solution

Probability that Amar would not be able to solve the puzzle = 1 - 2/7 = 5/7
Probability that Akbar would not be able to solve the puzzle = 1 - 3/5 = 2/5
Probability that Anthony would not be able to solve the puzzle = 1 - 4/9 = 5/9

Probability that puzzle is not solved = (5/7)*(2/5)*(5/9) = 10/63

Hence Probability that puzzle is solved = 1- 10/63 = 53/63
Option 4)

Correct Option: 4 Best Solution (3)

29 Oct 2020 Profit & Loss

Find the cost price of 1KG of Kaju Katli which is sold for Rs. 990 at a loss of 12%.

OPtion

1) 1100
2) 1025
3) 1075
4) 1125
5) 1175
6) 1000
7) 1145
8) 1150
9) 1225
10) None of these

Solution

If CP 100 SP 88
i.e. When SP 88, CP 100
when SP 880, CP = 100*990/88 = 1125

Correct Option: 4 Best Solution (0)

28 Oct 2020 Mensuration

A string is 148 cm long. It is cut into 3 pieces. The longest piece is 4 times as long as the middle-sized
piece & the shortest piece is 77 cm shorter than the longest piece. Find the length of the shortest piece (in cm).

OPtion

1) 12
2) 21
3) 13
4) 19
5) 28
6) 15
7) 23
8) 25
9) 27
10) None of these

Solution

Let the middle be x CM

Longest piece = 4x cm
Smallest piece = 4x - 77

x+4x+4x-77 = 148
9x = 225
x= 25
shortest piece = 4*25- 77 = 23 cm

Correct Option: 7 Best Solution (4)