M4maths Previous Puzzles

24 Nov 2011 corner

6 boys and 7 girls are available for a counselling. In how many ways, we can arrange them in a row, if middlest one is a boy and girls are sat on both the corners.

OPtion

1) 42*10!
2) 21*10!
3) 6*10!
4) 7*10!
5) 126*10!
6) 252*10!
7) 84*10!
8) 12*10!
9) 420
10) none of these

Solution

total number of methods = (6*7*6/2)*10! = 126*10!

Correct Option: 5 Best Solution (4)

23 Nov 2011 sphere

We have to melt a solid sphere of metal to form a cylinder of same radius. Which of the following is the possible value of radius to get a cylinder of integral height.

OPtion

1) 2 cm.
2) 4 cm.
3) 5 cm.
4) 8 cm.
5) 10 cm.
6) 12 cm.
7) 16 cm.
8) 20 cm.
9) more than one answers are correct
10) none of these

Solution

Volume of the solid sphere = 4(pi)(r^3)/3
volume of the solid cylinder = (pi)(r^2)h
on comparing these 2 volumes, we will get 4r = 3h
so only 12 cm. is possible answer out of the options given.

Correct Option: 6 Best Solution (0)

22 Nov 2011 sequence

next number of the sequence 4,7,11,17,27,45..............will be

OPtion

1) 49
2) 53
3) 64
4) 68
5) 75
6) 79
7) 86
8) 98
9) 102
10) none of these

Solution

4,7,11,17,27,45,x
series of difference 3,4,6,10,18,y
again sequence of difference 1,2,4,8,16
y = 18+16 = 34
x = 45+34 = 79

Correct Option: 6 Best Solution (0)

21 Nov 2011 flight

A plane starts at 11:00 (Indian time) and lands at 16:30 (America time) in America. If time difference between India and America is +5:30, then total teime of journey will be

OPtion

1) 5:30
2) 11
3) 12
4) 15
5) 16
6) 17
7) 19
8) 20
9) 21:30
10) none of these

Solution

Time difference = 16:30 - 11 = 5:30
and time difference between India and America is +5:30
so total difference of time = 5:30 + 5:30 = 11

Correct Option: 2 Best Solution (23)

18 Nov 2011 coin

Minimum no. of coins required to get the following 5 sums successfully
35, 46, 53, 69, 77
(You can consider imaginary coins of any cost)

OPtion

1) 6
2) 7
3) 8
4) 9
5) 10
6) 11
7) 12
8) 13
9) 14
10) none of these

Solution

coins required are 35, 46, 53, 69, 77
so answer is 5
option 10

Correct Option: 10 Best Solution (0)

17 Nov 2011 probability

There are 3 boxes. First box contains 4 red and 3 green, second box 3 red, 5 green and third box contains 4 red and 4 green balls. A ball has been selected and the selected ball is red. What will be the probability that the ball comes from first box.

OPtion

1) 1/81
2) 2/81
3) 12/81
4) 19/81
5) 25/36
6) 32/81
7) 40/81
8) 50/81
9) 27/100
10) 63/100

Solution

Probability = (4/7)/(4/7)+(3/8)+(4/8) = 32/81

Correct Option: 6 Best Solution (9)

16 Nov 2011 rail

width and thickness of two iron rails between two stations 5 km. apart are 20 cm. and 15 cm. If density of iron is 7200 kg/m^3, then total iron used to make the 2 rails will be

OPtion

1) 1560000 kg
2) 1080000 kg
3) 1240000 kg
4) 1540000 kg
5) 2160000 kg
6) 2540000 kg
7) 2820000 kg
8) 1860000 kg
9) 3040000 kg
10) none of these

Solution

total mass = number of rails * volume * density
= 2 * 5000 * 0.2 * 0.15 * 7200
= 10000 * 0.03 * 7200
= 300 * 7200 = 2160000 kg

Correct Option: 5 Best Solution (3)

15 Nov 2011 solve

(1+1(1+1(1+1(1+1(1+1))))) = ?

OPtion

1) 1
2) 2
3) 3
4) 4
5) 5
6) 6
7) 7
8) 8
9) 9
10) none of these

Solution

solve inner bracket first, then solve the complete expression

Correct Option: 6 Best Solution (14)

14 Nov 2011 deepawali

if diwali = 360, sweet = 60, cracker = 1260
then deepawali =

OPtion

1) 84260
2) 84920
3) 85360
4) 86580
5) 86920
6) 88640
7) 89200
8) 90300
9) 90720
10) none of these

Solution

in this question number represents the total number of words formed by letters of the associated word.

Correct Option: 9 Best Solution (0)

11 Nov 2011 solve

(2^3 + 3^4 + 4^5 + 5^6) - (6^5 + 5^4 + 4^3 + 3^2) = ?

OPtion

1) 7862
2) 8264
3) 8865
4) 16738
5) 8474
6) 5648
7) 9234
8) 7684
9) 6578
10) none of these

Solution

(2^3 + 3^4 + 4^5 + 5^6) = 16738
(6^5 + 5^4 + 4^3 + 3^2) = 8474
so difference = 16738 - 8474 = 8264

Correct Option: 2 Best Solution (21)