M4maths Previous Puzzles

09 Dec 2020 Percentage

Price of CNG first increased by 10% and then by 15%, and it becomes finally Rs.80. Find the initial rate of CNG.

OPtion

1) 65
2) 68
3) 64.5
4) 70.5
5) 63.24
6) 75.24
7) 73.24
8) 62.53
9) 64.82
10) None of the above

Solution

The initial amount = 80 x 100/110 x 100/115 = 80 x 100 x 100/ (110 x 115) = 63.24

Correct Option: 5 Best Solution (3)

08 Dec 2020 Area

A wall clock has its minute hand of length 21 cm. What area will it swept in covering 30 minutes?

OPtion

1) 545 cm^2
2) 637 cm^2
3) 742 cm^2
4) 693 cm^2
5) 540 cm^2
6) 620 cm^2
7) 342 cm^2
8) 603 cm^2
9) 303 cm^2
10) None of the above

Solution

Length will be the radius, so r = 21cm
Minute hand covers 360o in 60 minutes
So in 30 minutes it covers = 180 degree
Area of arc = angle it makes/360 * πr^2
So area covered = 180/360 * 22/7 * 21 * 21 = 693cm^2

Correct Option: 4 Best Solution (3)

07 Dec 2020 BOATS AND STREAMS

Vijay rows 1500m in 1350 seconds against the stream and returns in 15 minutes. His rowing speed in still water is?

OPtion

1) 5km/hr
2) 4km/hr
3) 7km/hr
4) 9km/hr
5) 6km/hr
6) 5.5km/hr
7) 6.5km/hr
8) 4.5km/hr
9) 7.5km/hr
10) None of the above

Solution

Rate upstream = (1500 / 1350) m/s = (150/135) m/s = = 10/9 m/s
Rate downstream = (1500 / 900)m/s = (15/9)m/s = 5/3 m/s
Rate in still water = ½ [ a+ b] = ½[10 / 9 + 5 /3] = ½[10 +15 / 9]
= ½[25/9] = 25/18 m/s = (25/18) * (18/5)km/hr
speed in still water = 5km/hr

Correct Option: 1 Best Solution (3)

04 Dec 2020 sequence

What is the next number of the following sequence
1, 4, 28, 160, .......

OPtion

1) 640
2) 850
3) 1230
4) 1010
5) 1600
6) 1750
7) 820
8) 1110
9) 1950
10) None of the above

Solution

(0+1)*1 = 1
(1+2)*2 = 6
(6+3)*4 = 36
(36+4)*5 = 200
(200+5)*6 = 1230

Correct Option: 10 Best Solution (0)

03 Dec 2020 Speed & Time

A man starts to run along a particular direction with a speed of 54 km./hours. After running upto a distance of 100 m, he increases his speed by 50 % of the initial speed, and runs upto 200 m. Total time taken by the man will be

OPtion

1) 10
2) 11.5
3) 12.5
4) 15.5
5) 16
6) 18.5
7) 20.5
8) 21
9) 22.5
10) None of these

Solution

54 km./hour = 54*5/18 = 15 m/s
81 km./hour = 81*5/18 = 22.5 m/s
so total time = (100/15)+(200/22.5) = 15.5 sec.

Correct Option: 4 Best Solution (3)

02 Dec 2020 Cost

Cost of 6 apple and 8 bananas is 460 rupee and that of 4 apple and 5 bananas is 300 rupee. Product of costs of 1 apple and 1 banana will be.

OPtion

1) 900
2) 960
3) 1000
4) 1020
5) 1140
6) 1200
7) 14140
8) 1560
9) 1800
10) None of these

Solution

According to the given condition
6a+8b=460 and 4a+5b=300
On solving we get b=20 and a=50 so a*b = 1000

Correct Option: 3 Best Solution (3)

01 Dec 2020 PROBABILITY

There are two bags. First contains 7 red and 5 violet balls whereas second contains 7 violet and 5 red balls. A ball is drawn at random from both the bags. Probability of both balls having same colour is

OPtion

1) 25/49
2) 35/144
3) 15/2
4) 35/7
5) 3/7
6) 37/25
7) 35/72
8) 1/9
9) 49/72
10) None of the above

Solution

(7/12)*(5/12) + (5/12)*(7/12) = 70/144 = 35/72

Correct Option: 7 Best Solution (3)

30 Nov 2020 Profit & Loss

Mohit got a profit of 40% in his investment of 7 lacs and loss of 12% in his investment of 8 lacs rupee. Find the overall profit in overall investment.

OPtion

1) 2.75
2) 2.33
3) 1.84
4) 1.62
5) 2.10
6) 1.76
7) 1.55
8) 3.86
9) 1.46
10) None of these

Solution

Total investment = 8 + 7 = 15 lacs
profit in first investment = 40*7/100 = 2.8 lacs
loss in second investment = 12*8/100 = 0.96 lacs
so overall profit = 2.8-0.96= 1.84 lacs

Correct Option: 3 Best Solution (1)

27 Nov 2020 Profit

he cost of 6 eggs is 30 rupee. If a plate 1.5 dozen eggs costs rupee 130 to shopkeeper, then what will be the profit of shopkeeper on selling a plate of egg?

OPtion

1) 10
2) 15
3) 20
4) 25
5) 30
6) 35
7) 40
8) 45
9) 50
10) none of these

Solution

The cost of 6 egg is 30 rupee.
Cost of 1 egg = 30/6 = 5
so selling cost of 1.5 dozen eggs = 18*5 = 90 rupee
so profit = 130-90 = 40 rupee.

Correct Option: 7 Best Solution (5)

26 Nov 2020 Linear equation

If x = 3-a and y = 4a+13, then for what value of a, x and y are equal?

OPtion

1) -6
2) -3
3) 6
4) 3
5) -4
6) 4
7) -7
8) 7
9) -2
10) None of the above

Solution

If x = y,
Then, 3 – a = 4a + 13
5a = -10
a = -2

Correct Option: 9 Best Solution (3)