If 100 cats kill 100 mice in 100 days, then 4 cats would kill 4 mice in how many days ?

Answer: Option B

Explanation:

Let Sunita's present age = x years
Then Reena present age = 2x years

Three years ago
(2x-3) = 3(x-3)
2x - 3 = 3x - 9
or x = 6

Reena age = 2x = 2*6 = 12 year.

Answer: Option B

Explanation:

I. matches of first player with other 5 players
II. matches of second player with 4 players other than the first player
III. matches of third player with 3 players other than the first player and second player.
IV. matches of fourth player with 2 players other than the first player, second player and third player.
V. matches of fifth player with 1 player other than the first player, second player, third player and fourth player.

So total matches will be 5+4+3+2+1 = 15

Answer: Option B

Explanation:

As from the question we have,
A = 3B --- (i)
c - 4 = 2(A+4) ---(ii)

Also, A + 4 = 31
or A = 31-4 = 27

Putting A = 27 in (i) we get
B = 9
Putting A = 27 in (ii) we get
C = 50

Answer: Option B

Explanation:

Let son's age be x then father's age is 3x
Five years ago, father's age = 3x-5 and son's age x-5
So, 3x-5 = 4(x-5)
=> 3x-5 = 4x-20
=> x = 15

Answer: Option D

Explanation:

If we read given question carefully, we get,
B+8 = C ---(i)
A-8 = C-3 ---(ii)
A+6 = 2D ---(iii)
B+D = 50 ---(iv)

Putting C = A -5 from (ii) into (i), we have :
B+8 = A-5 or A-B = 13 ---(v)

Putting D = 50-B from (iv) and (iii), we have :

A+6 = 100-2B or A+2B = 94 ---(vi)

Solving (v) and (vi), we get
B = 27 and A = 40