Posted by greeny on Friday, August 17, 2012 at 10:40pm.
If the first digit must be 2, and digits can be repeated, you can forget about the leading digit and just look for every THREE-digit integer (INCLUDING leading zeros) whose last digit isn't zero. That's every integer between 000 and 999 (of which there are 1000), excluding the 10% of them that end in zero (of which there are 100) - which makes 900 in total.
Only 1 choice for the 1st spot, 10 choices for the 2nd, 10 choices for the 3rd and 9 choices for the 4th
1x10x10x9 = 900
Related Questions
math - How many different positive four-digit integers can be formed if the ...
Math - i am a four digit number. all of my digits are different. my first digit ...
college math - How many different four-digit numbers can be formed from the ...
Mathematics - how many positive four- digit integers have 3 as their tens digit ...
math - The number uses every number 0-9 the numbers are used only once the ...
math-permutuation - a four digit serial number needs to be created using digits ...
math - i have a six digit question my 100 thousands is one less than my ones ...
math - There are 900 three-digit integers. The number of three-digit integers ...
math - i am a 5 digit palindromic number. My third digit is 5 more than my fifth...
Math - How many odd four-digit numbers, all of the digit different can be formed...
For Further Reading
