### Brain Teasers

# Copying Tapes

Marty and Jill want to copy three 60 minute tapes. They have two tape recorders that will dub the tapes for them, so they can do two at a time.

It takes 30 minutes for each side to complete; therefore in one hour two tapes will be done, and in another hour the third will be done. Jill says all three tapes can be made in 90 minutes. How?

It takes 30 minutes for each side to complete; therefore in one hour two tapes will be done, and in another hour the third will be done. Jill says all three tapes can be made in 90 minutes. How?

### Answer

Jill will rotate the three tapes. Let's call them tapes 1,2, and 3 with sides A and B. In the first 30 minutes they will tape 1A and 2A, in the second 30 minutes they will tape 1B and 3A (Tape 1 is now done). Finally, in the last 30 minutes, they will tape 2B and 3B.Hide Answer Show Answer

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## Comments

Simple but nice. Makes you think about efficient ways of doing things!

ya i wonder how much time ive wasted not thinking like that. great teaser

the reason i've rated it with a half-star is because the way of solving the teaser seemed rather straightforward.

Very nice, and for once I got it myself and almost immediately. However, I feel like the solution's wording could be a lot more straightforward.

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