The world.

10. Listen closely: 30 cows, and twenty-eight chickens. Say EIGHT and ATE. They sound the same. Therefore, it means 20 ATE chickens. 30-20=10, so 10 cows didn’t eat any chickens.

Sea Urchins.

The contents or the ten envelopes (in dollar bills) should be as follows: $1, 2, 4, 8, 16, 32, 64, 128, 256, 489. The first nine numbers are in geometrical progression, and their sum, deducted from 1,000, gives the contents of the tenth envelope.

A Rocking chair