Solution:

The watchman had been sleeping on the job. Otherwise, he would not have been dreaming.

Solution:

I am a Postbox

Remove as many letters as possible, still postbox remains the same.

Solution:

N for Nine

Solution:

33 seconds

The train takes 30 seconds to travel 1 mile, plus 3 seconds for the complete train to pass any point, making a total of 33 seconds.

Solution:

This is simply the numbers 2^0,2^1,2^2 ... that is 1,2,4,8,16... So for making 1000 kg we need up to 1, 2, 4, 8, 16, 32, 64, 128, and 512

Solution:

The missing number that fit in ? is 6.

The number in the middle of each triple is the same as the digits of either end's number when added together. 3+7=10=8+2 and so on.

Solution:

I have written 'your exact weight' on the paper.

Solution:

Each word rhymes with its numeric position in the list. (e.g. 'gun' rhymes with 'one'
etc.)

Solution:

Bookkeeper (00 kk ee)

Solution:

Twinkle and Rinki start on opposite sides of the river