1. Twelve pigs were eating a farmer’s groundnuts when he came out and shot dead one of them. How many remained in the field?

One, the dead one. The remaining eleven fled away!

2. One cat walked in front of two cats. One cat walked behind two cats. One cat walked between two cats. How many cats were there?

A popular Hindi version of this is

Three.

3. A crab is trying to climb a glass pane 30 cm high. It climbs 10 cm in 5 minutes and then rests for 5 minutes during which it slips back 5 cm. How much time will the crab take to reach the top?

45 minutes.

4. How many times does the digit 9 appear from 1 to 100?

20 times.

5. Every morning at 6, a ship leaves Tokyo for New York and at the same time, a ship leaves New York for Tokyo. It takes 10 days to complete the trip either way. If a New York bound ship starts from Tokyo on 15th of a month, how many Tokyo bound ships will it meet by the time it reaches New York?
(Ignore difference of timings between New York and Tokyo.)

21 ships in all.

6. A zoo has some birds and some beasts. There are 30 heads and 100 feet. Can you tell the number of birds and beasts?