Subject: How many two digit numbers... Fri Sep 11, 2009 9:11 pm
How many two digit numbers...
(a) are so that no digit is a zero Provide a solution.
(b) are so that each digit is even Provide a solution.
fremlinc
Posts : 9 Join date : 2009-09-17
Subject: Re: How many two digit numbers... Mon Sep 21, 2009 8:56 am
A 90 2 digit numbers (99-9)
B Well since 0 is not even 16
Archis that is to easy......
BhandarkarA
Posts : 85 Join date : 2009-09-11
Subject: Re: How many two digit numbers... Tue Sep 22, 2009 2:58 pm
Unfortunately both of those are incorrect. Let me rephrase the question.
How many two digit numbers have no digit as zero? How many two digit numbers have each digit even?
Think about the Fundamental Counting Principle, and remember that 0 is even.
fremlinc
Posts : 9 Join date : 2009-09-17
Subject: Re: How many two digit numbers... Thu Oct 01, 2009 8:41 pm
Well then I guess I was wrong
starting from 11 (because all the other numbers are 1 digit or have 0) 9x9 = 81
for the second one 20, 22, 24, 26, 28, 40, 42, 44, 46, 48, 60, 62, 64, 66, 68, 80, 82, 84, 86, 88 = 20
BhandarkarA
Posts : 85 Join date : 2009-09-11
Subject: Re: How many two digit numbers... Sat Oct 03, 2009 7:51 pm
Your method is correct for A.
There are 9 choices (any of the digits from 1-9) for the hundreds digit. As well, there are 9 choices (any of the digits from 1-9) for the hundreds digit.
Thus 9 times 9 is 81 as the answer for A.
Your answer is correct, but see if you can apply the Fundamental Counting Principle (what was used for the solution of A) for B instead of just listing them out.
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