From now on, I'll post the problems I find on the net that I find challenging, didn't get in the first try or didn't solve by the better method. Here's the first one!

NOTE: Whenever the problem is from MGMAT's CP of the Week, click on the link to go the original source of the problem.

NOTE: Whenever the problem is from MGMAT's CP of the Week, click on the link to go the original source of the problem.

**Question**

Xander, Yolanda, and Zelda each have at least one hat. Zelda has more hats than Yolanda, who has more than Xander. Together, the total number of hats the three people have is 12. How many hats does Yolanda have?

(1) Zelda has no more than 5 hats more than Xander.

(2) The product of the numbers of hats that Xander, Yolanda, and Zelda have is less than 36.

(1) Zelda has no more than 5 hats more than Xander.

(2) The product of the numbers of hats that Xander, Yolanda, and Zelda have is less than 36.

**Answer**

*x*for the number of hats Xander has,

*y*for the number of hats Yolanda has, and

*z*for the number of hats Zelda has. From the question stem, we know that

*x*<

*y*<

*z*and that

*x*+

*y*+

*z*= 12. Moreover, since each person has at least one hat, and people can only have integer numbers of hats, we know that

*x*,

*y*, and

*z*are all positive integers. With this number of constraints, we should go ahead and list scenarios that fit all the constraints. Start with

*x*and

*y*as low as possible, then adjust from there, keeping the order, keeping the sum at 12, and ensuring that no two integers are the same.

Scenario | x | y | z |

(a) | 1 | 2 | 9 |

(b) | 1 | 3 | 8 |

(c) | 1 | 4 | 7 |

(d) | 1 | 5 | 6 |

(e) | 2 | 3 | 7 |

(f) | 2 | 4 | 6 |

(g) | 3 | 4 | 5 |

*y*. Now, we turn to the statements.

Statement (1): INSUFFICIENT. We are told that

*z*–

*x*is less than or equal to 5. This rules out scenarios (a) through (c), but the last four scenarios still work. Thus,

*y*could be 3, 4, or 5.

Statement (2): INSUFFICIENT. We are told that

*xyz*is less than 36. We work out this product for the seven scenarios:

(a) 18

(b) 24

(c) 28

(d) 30

(e) 42

(f) 48

(g) 60

We can rule out scenarios (e) through (g), but (a) through (d) still work. Thus,

*y*could be 2, 3, 4, or 5.

Statements (1) and (2) together: SUFFICIENT. Only scenario (d) survives the constraints of the two statements. Thus, we know that

*y*is 5.

The correct answer is (C): BOTH statements TOGETHER are sufficient to answer the question, but neither statement alone is sufficient.

## No comments:

Post a Comment