Question

Aa new colony was built and the builder gave contract to a sign maker to a number the buildings from number 1 to 100. How many zeroes will he need

Answer 1

Look at it in sets of 10. If he needs to number the buildings from 1 to 100, he will need 10 sets of 10 numbers each. 

The first set will be from 1 to 10, 

the second set from 11 to 20,

the third one from 21 to 30 and so on. 

For each set, he will need only one 0 (at the end of the set). 

So, from 1 to 90, he will need nine zeroes. However, in the last set, the last number is 100, which has 2 zeroes. 

Hence, the total number of zeroes that he will need is 9+2= 11.