In the morning, Barry flied from home to school in 20 minutes. In the afternoon, he and Adam talked to each other while flying, so the time increased to 30 minutes. Find the average flying rate (km/h) of Barry. Assume that the distance between home and school is 4000m

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19) In the morning, Barry flied from home to school in 20
minutes. In the afternoon, he and Adam talked to each
other while flying, so the time increased to 30 minutes.
Find the average flying rate (km/h) of Barry. Assume that
the distance between home and school is 4000m.