Basic Puzzles Harder Puzzles Sticks, Coins & More... Funny Riddles & Puzzle Jokes Mathematical Problems Harder Mathematical Problems Logical Puzzles Brainteasers Complex Problems Brain Tests & Experiments Quizzes
A short introduction Cookie policy Links

Solution to: Postman Pat

If postman Pat had delivered mail three times at each house, then the total sum of the house numbers per day would be (1+2+3+4+5+6+7+8+9+10)×3=165. Now that sum is 18+12+23+19+32+25=129. The difference is 165-129=36; divided by 3 this is 12. The sum of the house numbers where no mail was delivered is therefore 12. The following combinations are possible:


Each day, at four houses the mail was delivered. On Tuesday, the sum was 12. 12 can only be made from four house numbers in two ways:


The same holds for Friday with the sum of 32:


From this, we can conclude that the house numbers 1, 2, 9 and 10 for sure have received mail, which means that the combinations 2+10 and 3+9 are not possible. In addition, the combination 5+7 is not possible, because mail was delivered either at house 5 or at house 7. Thus the only remaining solution is: houses 4 and 8.

N.B.: there are various possibilities for the actual post-delivery of the whole week. For example:

Mondayhouses 1, 3, 5 and 9
Tuesdayhouses 1, 2, 3 and 6
Wednesdayhouses 1, 5, 7 and 10
Thursdayhouses 2, 3, 5 and 9
Fridayhouses 6, 7, 9 and 10
Saturdayhouses 2, 6, 7 and 10

Copyright © 2002 E.R. van Veldhoven. All rights reserved.

Back to the puzzle
This website uses cookies. By further use of this website, or by clicking on 'Continue', you give permission for the use of cookies. If you want more information, look at our cookie policy.