Joe and Andrea want to copy three 60-minute cassette tapes. They have a 2-cassette recorder to copy the tapes, allowing them to copy two tapes at a time. Each side takes 30 minutes to be copied, so two tapes can be copied in an hour and the third will take another hour. Andrea bets Joe she can copy all three tapes in 90 minutes. Does she win the bet?
In the first 30 minutes Andrea copies the A sides of tape 1 and 2. In the second 30 minutes, she copies tape 1 side B and tape 3 side A (finishing Tape 1). In the last 30 minutes, she copies tape 2 side B and tape 3 side B.
I give you a group of three. One is sitting down, and will never get up. The second eats as much as is given to him, yet is always hungry. The third goes away and never returns.
The name ABRAHAM can be changed into a word for a primitive musical instrument by replacing each letter with a different letter. The repeated letters (A is this case) must be replaced with the same replacement letter in the new word.
A variation of this brain teaser includes laser printers (they were invented by Gary Starkweather) and bulletproof vests (invented by Casimir Zeglen using silk, though modern vests use Kevlar, so it’s halfway right).