How do you tell when you run out of invisible ink? 
Math Puzzle AnswerYou’re looking at the answer to one of our math puzzles. There are several other puzzles for you to solve. Please click to find all our math puzzles.
CD Track Lengths  AnswerThe lengths of the tracks are (5, 7, 17, 19), (7, 11, 13, 23) and (7, 13, 17, 23). None of the track lengths can be 2 because any sum of the three different primes, including 2, would not be prime. Therefore, the track lengths must be chosen from the 13 primes between 3 and 43. To get the answer, find all three prime combinations whose sum is a small enough prime that another prime (larger than any of the three) can be added to result in a sum of 60 or less. There are 14 such combinations: (3, 5, 11), (3, 5, 23), (3, 7, 13), (3, 7, 19), (3, 11, 17), (5, 7, 11), (5, 7, 19), (5, 11, 13), (5, 13, 19), (7, 11, 13), (7, 11, 19), (7, 13, 19), (7, 13, 17) and (11, 13, 17). If you try all possible fourth primes with those combinations, you'll find that the only possibilities which meet the requirements (sum of 60 or less and sum of any three is a prime) are the answers given above.


Home
Brain Teasers
Cryptic Math Puzzles
Logic Puzzles
Math Puzzles
Hard Math Puzzles
Word Picture Puzzles
Logic GamesPlay Mastermind Same Game Play ShisenSho Other GamesCar Games Skiing Games Football Games Free Kid Puzzles Magic Triangle Game US Jokes Hilarious Blonde Jokes I have Learned... Play Javaroids Kid Games Play Black Viper FastLap Dublin Driving Game Wermz Online Game Classic Online Games Stereogram Pictures Weird Illusions Visual Illusions
Report A Broken Link Contact Information 


BrainFun.com 
Site Map 
Terms of Use 
Privacy & Security 
Contact Us 
Purchase Agreement 
Send Feedback 