School-Safe Puzzle Games

## Clock Counting Puzzle

This brain teaser comes courtesy of www.braingle.com:

Three-year-old Sam has just learned to count to 30! He especially likes to read the clock when the numbers are in order. For example, he likes 3:45, which he sees not as three forty-five, but as three, four, five. Can you find all the times when the numbers on a clock are in sequential order?

Will post the answer in a day or two in the ‘comment’ section.

### 1 Comment to “Clock Counting Puzzle”

1. RLP | Profile

Here’ s the answer from http://www.braingle.com:

A 12-hour clock has these 9 possibilities:

1:23 (one, two, three)
2:34
3:45
4:56
9:10 (nine, ten)
10:11
11:12
12:13
12:34 (one, two, three, four)

However, Robert Dawson was kind enough to email and let me know the above answer may not be entirely complete! (note the backward sequences as well as the possibility of double digit single numbers, for a total of 34)

> singles forward:
> 12:34
> 1:23
> 2:34
> 3:45
> 4:56
>
> singles backward:
> 1:09
> 2:10
> 3:21
> 4:32
> 5:43
> 6:54
>
> doubles forward:
> 1:02
> 2:03
> 3:04
> 4:05
> 5:06
> 6:07
> 7:08
> 8:09
> 9:10
> 10:11
> 11:12
> 12:13
>
> doubles backward:
> 12:11
> 11:10
> 10:09
> 9:08
> 8:07
> 7:06
> 6:05
> 5:04
> 4:03
> 3:02
> 2:01
> 1:00

When preparing for the SAT years ago, I remember there being some controversy about some of the math questions have more than 1 right answer…