+0  
 
-3
102
5
avatar+-291 

How many integers between $100$ and $150$ have three different digits in increasing order? One such integer is $129$.

 Mar 30, 2020
edited by helpppp  Mar 30, 2020
 #1
avatar+626 
+1

I recommend you just list them out.

By the way this would make a fun, short, coding challenge!

 

Organize the list by the tength's place:

 

 

1
2
3
4
5
0 is eliminated because the first digit is larger than 0 as the second digit

 

Now list each number in increasing order in the given table.

 Mar 30, 2020
 #2
avatar
+1

123  124  125  126  127  128  129  134  135  136  137  138  139  145  146  147  148  149>>=18 such integers  

 Mar 30, 2020
 #4
avatar
+1

It is 18

 Mar 31, 2020

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