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Find the number of five-digit numbers which are not divisible by 5?

Sagot :

Answer:

72000

Step-by-step explanation:

First five digit number is 10000

And the last five digit number is 99999.

There are 99999-10000+1 five digits in all.

That simplifies to 89999+1=90000.

Any number whose units digit is 5 or 0 is divisble by 5.

10000 is the first five digit number that is divisble by 5.

10000+5k where k is a positive integer can be used to find any after.

The last five digit number divisible by 5 is 99995. What is k then?

10000+5k=99995

5k=89995

k=89995/5

k=17999

How many 5 digit numbers are divisble by 5?

So the first one happens at k=0 and the last one happens at k=17999.

How many numbers is that? 17999+1=18000.

So the number of 5 digit numbers that aren't divisble by 5 is 90000-18000=72000