TestMagic Forums - View Single Post - how many integers between have tens digit 1 and unit digit 3 ?

ibelieveican · 2008 October 5th, 09:10 PM

Good Q
IMO E

Here is how.
324700 to 458600

Let us consider intervals now

1. 324a13 what are the values a can take. 7, 8, 9 so 3C1
2. 32ab13 a can take values 5, 6, 7, 8, 9 ( 4 is already considered in 1) 5C1
b can take values from 0 to 9 so 10C1....5c1X10C1
3. 3abc13.. a takes values 3 to 9 so 7C1 b and c takes values 0 to 9 so... 7C1X10C1X10C1

now we need to do the same thing with 458600 and I get E

Hope I made sense

2008 October 5th, 09:10 PM	#2 (permalink)
ibelieveican Within my grasp! Join Date: Sep 2008 Posts: 138	Good Q IMO E Here is how. 324700 to 458600 Let us consider intervals now 1. 324a13 what are the values a can take. 7, 8, 9 so 3C1 2. 32ab13 a can take values 5, 6, 7, 8, 9 ( 4 is already considered in 1) 5C1 b can take values from 0 to 9 so 10C1....5c1X10C1 3. 3abc13.. a takes values 3 to 9 so 7C1 b and c takes values 0 to 9 so... 7C1X10C1X10C1 now we need to do the same thing with 458600 and I get E Hope I made sense