M4maths Previous Puzzles

15 Apr 2010 Possible combination?

A three digit number is equal to the product of its three digits. How many such numbers are possible?

OPtion

1) 0
2) 1
3) 2
4) 3
5) 4
6) 5
7) 6
8) 7
9) 8
10) 9

Solution

According to the given condition

100x + 10y + z = xyz

(100 – yz)x + 10y +z = 0
x = (10y + z) / (yz – 100)
For every integral value of y and z ranging from 0 to 9, x is negative. Hence no such number is possible.

Correct Option: 1 Best Solution (11)

14 Apr 2010 Card Selection

Total number of methods of selecting 6 cards out of 10 different cards is x,
and total number of methods of selecting 6 cards out of 10 similar cards is y. Difference of x and y is

OPtion

1) 1
2) 210
3) 209
4) 60
5) 59
6) 0
7) 8
8) 69
9) 225
10) 5

Solution

Total number of methods of selecting 6 cards out of 10 different cards is
10*9*8*7*6*5/6*5*4*3*2*1 = 210
And total number of methods of selecting 6 cards out of 10 similar cards is only 1
Difference is 209

Correct Option: 3 Best Solution (9)

13 Apr 2010 Next Number?

Next number will be?
1 3 16 1320 ....?

OPtion

1) 13231376
2) 1350
3) 1340125
4) 13501366
5) 13161325
6) 12561842
7) 13201
8) 2684
9) 13123416
10) 13201316

Solution

1 = 1
1+2 =3
13+3 = 16
1316+4 = 1320
13161320+5 = 13161325

Correct Option: 5 Best Solution (9)

12 Apr 2010 Sum of Roots

If {7/x} + {(x+3)/2} = 6, then sum of all the possible values of x is?

OPtion

1) 8
2) 7.5
3) 6
4) 9
5) 7
6) 4.5
7) 2
8) 6.8
9) 9.8
10) 3

Solution

{7/x} + {(x+3)/2} = 6
implies (14+x2+3x)/2x = 6
implies (14+x2+3x) = 12x
implies x2-9x+14 = 0
implies x = 2, 7
hence sum of values of x = 2+7 = 9

Correct Option: 4 Best Solution (19)

09 Apr 2010 Train Puzzle

A train travels from A to B with speed 20 km/hrs and from B to A with speed 30 km/hrs.
Average speed (in km/hrs) of the train for the whole journey is

OPtion

1) 21
2) 25
3) 24
4) 27
5) 26.5
6) 24.66
7) 25.66
8) 28
9) 29
10) 23.5

Solution

Let the distance between A to B is L km.
Total distance covered = 2L km.
Time taken in the journey = (L/20) + (L/30) = 50L/600 = L/12
Hence average speed = 2L/(L/12) = 24 km/hrs

Correct Option: 3 Best Solution (12)

08 Apr 2010 Find the value of equation

If (4x-3y)/ (4x+3y) = 3/5, then (3x+2y)/ (3x-2y) is?

OPtion

1) 6/13
2) 5/3
3) 1/2
4) 11/8
5) 8/11
6) 7/11
7) 9/14
8) 14/9
9) 11/7
10) 13/6

Solution

(4x-3y)/(4x+3y) = 3/5
(4x-3y)+(4x+3y)/ (4x-3y)-(4x+3y) = 3+5/3-5
8x/-6y = 8/-2
x/y = 3/1
3x/2y = 9/2
(3x+2y)/(3x-2y) = 11/7

Correct Option: 9 Best Solution (8)

07 Apr 2010 Rank of ABDUL in dictionary?

The rank of the word ABDUL in the dictionary of all the words formed by the letters of the word ABDUL is?

OPtion

1) 1
2) 12
3) 120
4) 37
5) 2
6) 24
7) 28
8) 49
9) 29
10) 100

Solution

A, B, D are in the correct sequence in the given word, but U and L are in reverse positions, hence rank is 2.

Correct Option: 5 Best Solution (14)

06 Apr 2010 Prime Numberrs

Sum of all the prime numbers from 1 to 40 is ?

OPtion

1) 186
2) 195
3) 194
4) 192
5) 190
6) 197
7) 184
8) 180
9) 178
10) 174

Solution

prime numbers from 1 to 40 are
2,3,5,7,11,13,17,19,23,29,31,37

Correct Option: 6 Best Solution (12)

05 Apr 2010 Salt strength?

Strength of a solution of salt is 60 gm/litre. After adding 5 litre of water, the new strength in gm/litre will be.

OPtion

1) 16
2) 20
3) 15
4) 12
5) 10
6) 14
7) 30
8) 60
9) 25
10) 36

Solution

Initial strength = 60 gm/1 litre
After adding 5 litre of water strength = 60 gm/ 6 litre = 10 gm/ 1 litre

Correct Option: 5 Best Solution (11)

02 Apr 2010 3 Distinct Number

There are 3 distinct numbers whose sum and product are equal. The sum of cubes of the three numbers is

OPtion

1) 12
2) 28
3) 15
4) 36
5) 20
6) 54
7) 37
8) 52
9) 78
10) 64

Solution

These 3 numbers are 1, 2 & 3
Sum of their cubes is 1 + 8 + 27 = 36

Correct Option: 4 Best Solution (14)