#math trivia #123 solution

We’ll start by assuming that single-digit numbers have their single digit in increasing order.  9 numbers so far.

Among the two-digit numbers, 36 are in increasing order:  8 in the 10s, 7 in the 20s, …, up to 1 in the 80s; 8+7+…+1 = 36.

The 100s and 200s are similar to the two-digit numbers, except that we lose the 10s in the first case and the 10s and 20s in the second.  Another 28 + 21 numbers.

In the 300s, we have just the 5 in the 40s and the 4 in the 50s.  None in the 60s, whether a leap year or not; 367 would be the first one.

Total:  9 + 36 + 28 + 21 + 5 + 4 = 103.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s