Math Puzzles Questions

Non collision can happen only when all the cars move in same direction.

That is either all cars moving in clockwise direction or all cars moving in anti clockwise direction.
P(all cars not colliding)

= P(all cars moving in the same direction)

= P(all cars moving in clockwise direction)  +  P(all cars moving in anticlockwise direction)

= [p(A --> C) x p(C --> B) x p(B --> A)]  +  [p(A --> B) x p(B --> C) x p(C --> A)]

= [1/2 x 1/2 x 1/2] + [1/2 x 1/2 x 1/2]

= 1/8 + 1/8

= 1/4

In the given puzzle the logic is

2 x 1 + 1 = 2 + 1 = 3

3 x 2 + 2 = 6 + 2 = 8

4 x 3 + 3 = 12 + 3 = 15

5 x 4 + 4 = 20 + 4 = 24

6 x 5 + 5 = 30 + 5 = 35

Similarly,

7 x 6 + 6 = 42 + 6 = 48

7 = 48.

  Zero. You are selecting names from the list, so they are all listed.

Let the required number be 'N'

given that its quarter i.e; N/4 exceeds its double i.e, 2N by 7

=> N/4 + 7 = 2N

=> N + 28 = 8N

7N = 28

N = 4.

(1+9+6+8+3) x (1+9+6+8+3) x (1+9+6+8+3) = 19683

Except 142 all are divisible by number '7'.

Let that something be 'x'

From the given data,

x + x/5 = 21

5x + x/5 = 21

6x = 21 x 5

=> x = 17.5

Hence, that something is x = 17.5.

In the given puzzle, the logic behind is

9 = 72 => 9 x 8 = 72

8 = 56 => 8 x 7 = 56

7 = 42 => 7 x 6 = 42

6 = 30 => 6 x 5 = 30

5 = 20 => 5 x 4 = 20

Similarly,

4 = 12 => 4 x 3 = 12

3 = 6 => 3 x 2 = 6