A student got twice as many sums wrong as he got right. If he attempted 48 sums in all, how many did he solve correctly ?

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

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:

Suppose boy got x sums right and 2x sums wrong,
then,
x+2x = 48
=> 3x = 48
=> x = 16

Answer: Option A

Explanation:

First of all, calculate LCM of 5, 6, 7 and 8 which is 840.
Suppose Number is K
then 840 * K + 3 is divisible by 9.
If K = 1, number = (840 × 1) + 3 = 843 which is not divisible by 9

If K = 2, number = (840 × 2) + 3 = 1683 which is divisible by 9

So 1683 is correct answer.