Question

A new colony was built and builder gave contract to a sign maker to number the buildings from numbr 1 to 500.how many zeroes will we need

Answer 1

Around 90.

The units column i.e., 10,20,30... will contain 50 zeros. And numbers like 101, 201, 302.... will have 40 zeros and it would sum up to 90. 

Answer 2

9 zeroes from 1 to 90. 
12 zeroes from 100 to 110.
8 zeroes from 111 to 190.
12 zeroes from 200 to 210.
8 zeroes from 211 to 290.
12 zeroes from 300 to 310.
8 zeroes from 311 to 390.
12 zeroes from 400 to 410.
8 zeroes from 411 to 490.
2 zeroes from 491 to 500.

Therefore the sum is 9+4(12+8)+2
                               = 11+4(20)
                               = 11+80
                               = 91 zeroes.