Q: Peter has 15 birds. 1/3 are ducks. The rest are chickens and require special feed that costs $2 per bird. How much does it cost to feed the chickens?
A: 2 / 3 of the birds are chickens because 1 - (1 / 3) = 2 / 3. He has 10 chickens because 15 x (2 / 3) = 10. It will cost $20 to feed them because 10 x 2 = 20. The answer is 20.

Q: In Hawaii, they normally get an average of 2 inches of rain a day. With 100 days left in the year, they've gotten 430 inches of rain. How many inches on average do they need to finish the year with the normal average?
A: They need 730 inches of rain a year to average 2 inches a day because 365 x 2 = 730. They need 300 more inches because 730 - 430 = 300. They need 3 inches a day because 300 / 100 = 3. The answer is 3.

Q: Last year, Peter organized a Fun Run for his community project and 200 people signed up. Forty people did not show up to run. This year, there will be twice as many runners as last year. How many people will run this year?
A:
There were 200 - 40 = 160 runners last year. Therefore, there will be 2 x 160 = 320 runners this year. The answer is 320.