A Builder wishes to buy plastic numerals to screw to the front doors of a street of 100 houses. The houses are on both sides of the street so all numbers from 1 to 100 are needed. To buy the number “64”, for example, the builder has to buy a six and a four. In fact, the builder has to buy a total of 192 numbers. In purchasing the plastic numbers, how many nines must the builder buy?
How Many Nines