Answer the following question, with explanation first.
Flies are Betty's frog's favorite food. Every day the frog eats 2 flies. Betty puts the flies she finds in a bottle. In the morning Betty catches 5 flies inside a bottle, and in the afternoon she catches 6 more, but when she removes the lid, one escapes. Betty wants to gather the whole week's food for her frog. How many more flies does she need?

4
The frog eats 2 flies / day * 7 days / week = 14 flies a week.

Betty catches flies in the morning and in the afternoon, for a total of 5 flies + 6 flies = 11 flies.

But 1 fly escapes, leaving 11 flies - 1 fly = 10 flies.

To get her frog's food for the whole week, Betty needs 14 flies - 10 flies = 4 more flies.

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The answer is 4