Basically the funda is that in a base n, we have n digits from 0 to n-1…so if we have a system which incorporates all possible variants using n digits (as here) we can map it to base n. So if I ask you to make all possible numbers using only 0, 3 and 5 you could map it to base 3 and say the digits 0, 1 and 2 are equivalent to the 0, 3 and 5 of our given system.
Because 5 is getting skipped, so the digit 6 on the meter is equivalent to a 5 in base 9 (see the table) Had the meter shown 4679 we would have taken it as 4568…
CAT-holics 
Sir i did not get the first question … How does the meter skipping digit 5 related to base 9
It is similar to the 3rd question in this post, Girish: https://crackthecat.wordpress.com/2013/06/13/base-systems-examples/#comments
Basically the funda is that in a base n, we have n digits from 0 to n-1…so if we have a system which incorporates all possible variants using n digits (as here) we can map it to base n. So if I ask you to make all possible numbers using only 0, 3 and 5 you could map it to base 3 and say the digits 0, 1 and 2 are equivalent to the 0, 3 and 5 of our given system.
regards
J
Thank you sir… good one as always..!!!
Sir, I didn’t get why in the 1st question you have taken 3015 for calculation instead of 3016??
Because 5 is getting skipped, so the digit 6 on the meter is equivalent to a 5 in base 9 (see the table) Had the meter shown 4679 we would have taken it as 4568…
regards
J
now i get it….thank you sir 🙂