SOLUTION: Identify properties of counting numbers. Find the number of four-digit counting numbers containing at least one zero, under each of the following conditions. (a) Repeated digit

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Question 843623: Identify properties of counting numbers. Find the number of four-digit counting numbers containing at least one zero, under each of the following conditions.
(a) Repeated digits are allowed.
(b) repeated digits are not allowed.
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

Find the number of four-digit counting numbers containing at least one zero:

All minus  four-digit counting numbers with no zero

Note: zero cannot be the first digit

(a) Repeated digits are allowed. 9%2A10%2A10%2A10-+9%2A9%2A9%2A9 

(b) repeated digits are not allowed. 9%2A9%2A8%2A7+-+9%2A8%2A7%2A6+