Solution:

They use the bricks and dirt from the tunnel to stand on it.

Solution:

Steps:
1) Light fire on first bar from both the ends and second bar from one end.

2) After 30 seconds(when first bar gets completely burned out) , burn the second bar from second end as well.

3) When second run completely gets burned , you know its 45 seconds.

Solution:

The mules is moving in circular path and hence outside legs travels more distance than inner legs.

Solution:

Hhe hung herself using big Ice slabs , which are now now melted and hence puddle of water.

Solution:

1. We open the cupboard, put the dinosaur in the cupboard and close it.
2. We should open the cupboard, take the dinosaur out of cupboard, put the tiger in and close it.
3. The tiger, hes still in the cupboard
4. You swim across the lake as all the crocodile are at the party.

Solution:

2 minutes (duration between 9:59 and 10:01)

Solution:

12345679

12345679 × 9 = 111111111 (only 1s)
12345679 × 18 = 222222222 (only 2s)
12345679 × 27 = 333333333 (only 3s)
12345679 × 36 = 444444444 (only 4s)
12345679 × 45 = 555555555 (only 5s)

Solution:

12:00

both minute and hour clock lie exactly between the number one and two in the number.

Solution:

5 leopard and one sheep

since all animal are rational , once 1st leopard eats the sheep all the rest of leopard would know about this.

Solution:

None

The sum of numbers from 0-9(0,1,2,3,4,5,6,7,8,9) is 45 and therefore can be divisible by 3 and 9.