What are some fun 4th-grade brain teasers?

Brain teasers for fourth grade are usually related to math, word play or riddles. An example of a word play teaser is the following: What do you get if you cross an automobile with a household pet? You get a carpet. The words "car" plus "pet" fulfill the question.

An example of a math brain teaser is the following: Mrs. Ortiz baked a batch of cookies that four children shared equally. She baked a second batch twice the size of the first, but she kept back six before serving the rest to the children. Mr. Ortiz ate two cookies from the children's serving. Each child ate three more cookies and left four on the tray. How many cookies were in the first batch and the second batch? The answer is that there were 12 cookies in the first and 24 cookies in the second. Fourth graders arrive at this answer by multiplying the four children times the three cookies they ate as a second serving, adding the two cookies Mr. Ortiz ate, the four they left behind and the six Mrs. Ortiz kept back. That gets them to 24. The first batch was half that size, so 12.

An example of a riddle is the following: No sooner spoken than broken. What is it? The answer is silence. As soon as a person speaks, the silence is broken.