SOLUTION: An increasing number has its digits increase in size from left to right. For example 24589 is an increasing number. How many four digit increasing numbers are there?

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Question 1133637: An increasing number has its digits increase in size from left to right. For example 24589 is an increasing number. How many four digit increasing numbers are there?
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
choose 4 out of 10
there can be ONLY 1 way the 4 can be arranged in ascending order, so selection is what we are looking for and NOT arrangements

10C4=10%21%2F%286%214%21%29=%2810%2A9%2A8%2A7%29%2F%284%2A3%2A2%29=210

BUT it contains numbers with 0 in thousands digit making these 3-digit numbers
so 9C3=9%21%2F%286%213%21%29=%289%2A8%2A7%29%2F%283%2A2%29=84.......deduct it from 210

210-84=126
your ans: there is 126 four digit increasing numbers