**A rectangular wooden board has a length-to-width ratio of 2:1. If both the length and the width are decreased by 2 inches, the ratio becomes 2.5:1. What is the width of the original board?**

*Solution to yesterday’s problem:*

The problem asks for prime numbers less than 50. Let’s list these prime numbers:

2 | 3 | 5 | 7 |

11 | 13 | 17 | 19 |

23 | 29 | ||

31 | 37 | ||

41 | 43 | 47 |

Now we’ll strike through the numbers that don’t satisfy “P+1 divisible by 3” and emphasize the ones that do.

2 |
5 |
||

11 |
17 |
||

23 |
29 |
||

41 |
47 |

There are 8 prime numbers that satisfy the condition, and 7 that do not – 15 numbers total. So the probability that a number chosen from this group will satisfy the condition is *8/15*.

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