M4maths Previous Puzzles

17 Dec 2021 Number

The total marks obtained by Ramesh in Hindi, English and Mathematics together is 90 more than the marks obtained by him in English. What are the average marks obtained by him in Hindi and Mathematics together?

OPtion

1. 60
2. 65
3. 45
4. 48
5. 50
6. 55
7. 42
8. 46
9. 62
10. None of the above

Solution

Let, marks got in physics, chemistry and mathematics are H, E and M.
H + E + M = E + 90
∴ H + M = 90
H + M/2 = 45.

Correct Option: 3 Best Solution (1)

16 Dec 2021 value of k

For what value of k, the system of equations 3x + 6y = 8 and 6x + 12y = k represents, coincident lines?

OPtion

1. 12
2. 26
3. 22
4. 24
5. 18
6. 16
7. 20
8. 21
9. 23
10. None of the above

Solution

If the given system of equations represents coincident lines
a1/a2 = b1/b2 = c1/c2
3/6 = 6/12 = 10/k
K = 10 x 12 / 6 = 20

Correct Option: 6 Best Solution (3)

15 Dec 2021 straight line

How many straight lines can be drawn with 26 points on a plane of which no points are collinear?

OPtion

1. 125
2. 153
3. 255
4. 225
5. 325
6. 275
7. 230
8. 330
9. 335
10. None of the above

Solution

The required number of straight lines
= n (n – 1)/2 =
= 26 (26 – 1)/2
= 26 * 25 / 2
= 650/2
= 325

Correct Option: 5 Best Solution (3)

14 Dec 2021 Rice Price

The cost (per Kg) of 3 qualities of rice are 45, 42 and 35 respectively. The cost (per Kg) of a mixture of 10 Kg of first, 8 Kg of second and 7 Kg of third will be

OPtion

1) 39.86
2) 39.64
3) 40.46
4) 41.24
5) 42.34
6) 42.38
7) 43.46
8) 43.12
9) 44.42
10) none of these

Solution

Total cost of the mixture:
(10*45)+(8*42)+(7*35)=Rs.1031
Total Qty of the mixture:(10+8+7)=25kg.
Cost per Kg. of mixture=1031/25=Rs.41.24

Correct Option: 4 Best Solution (0)

13 Dec 2021 Sum

The sum of a number of two digits and the number obtained by exchanging the places of digits is 110. If units place is 4 more than the tens place in the given number, then product of two digits of the number will be

OPtion

1) 64
2) 46
3) 37
4) 73
5) 19
6) 91
7) 82
8) 28
9) 21
10) none of these

Solution

let no be yx
given x-y=4...(1)
xy+yx=110 equivalent to x+y+10(x+y)=110
i.e. x+y=10...(2)
solving (1)&(2) we get x=7,y=3
i.e. the no. is 37
product will be 3*7=21

Correct Option: 9 Best Solution (3)

10 Dec 2021 Length of bridge

A train 130 m long passes a bridge in 21 seconds moving at a speed of 90 Km/h. Find out the length of the bridge

OPtion

1. 395 m.
2. 420 m.
3. 425 m.
4. 380 m.
5. 386 m.
6. 352 m.
7. 365 m.
8. 368 m.
9. 399 m.
10. None of the above

Solution

We have, speed of the train
= (length of the train + length of the bridge) / time taken in crossing the bridge
⇒ 5/18 x 90 = (130 + length of the bridge)/ 21
= 450 x 21 = 2340 + 18 (length of the bridge)
= 9450 – 2340 = 18 (length of the bridge)
∴ Length of the bridge
= 7110 / 18 = 395 m.

Correct Option: 1 Best Solution (6)

09 Dec 2021 Class

The average weight of 31 students of section A of a class is 53 Kg, whereas the average weight of 27 students of section B of the same class is 55 Kg. Find out average weight of all the 58 students of the class

OPtion

1. 59.3 kg
2. 55.5 kg
3. 52.6 kg
4. 53.9 kg
5. 55.6 kg
6. 58.2 kg
7. 54.2 kg
8. 53.1 kg
9. 60.2 kg
10. None of the above

Solution

Here, n1 = 31, n2 = 27, x = 53, and y = 55.
∴ Average weight of all the 58 students = (n1x + n2y)/(n1+n2)
= [(31x53) +(27x55)]/ (31+27)
= (1643 +1485)/58
= 53.9kg

Correct Option: 4 Best Solution (3)

08 Dec 2021 AVERAGE

The average of x numbers is 5x. If x − 2 is subtracted from each given number, what will be the new average?

OPtion

1. 2X + 2
2. 2X + 1
3. 2X - 1
4. 2X – 2
5. 4X + 1
6. 4X + 2
7. 4X – 1
8. 5X + 2
9. 5X + 1
10. None of the above

Solution

The new average = x − a
=5x − (x − 2)
= 4x + 2.

Correct Option: 6 Best Solution (1)

07 Dec 2021 cistern

A pipe can empty a cistern in 40 minutes. Find the time in which 3/4 part of the cistern will be emptied.

OPtion

1. 25 minutes
2. 28 minutes
3. 32 minutes
4. 40 minutes
5. 30 minutes
6. 36 minutes
7. 38 minutes
8. 32 minutes
9. 29 minutes
10. None of the above

Solution

1/40 part of the cistern is emptied in = 1 minute.
∴ 3/4 part of the cistern is emptied in
= 40 × 3/4 = 30 minutes.

Correct Option: 5 Best Solution (2)

06 Dec 2021 Gain

A shopkeeper professes to sell his goods on cost price, but uses 750 gm, instead of 1.2 Kg. What is his gain %?

OPtion

1. 25%
2. 30%
3. 33.33%
4. 20%
5. 40%
6. 55%
7. 50%
8. 60%
9. 52%
10. None of the above

Solution

Here, cost price of 1200 gm is equal to selling price of 750 gm,
∴ % gain = [(m – n)/ n] × 100
= [(1200 – 750)/ 100] x100
= 450/ 750 × 100 = 60%

Correct Option: 8 Best Solution (4)