Christmaths Advent Calendar 2013: Day 18

This year’s Christmaths Advent Calendar will have a question for every day in December up to and including Christmas Day, each one featuring a new mathematical challenge.

Father Christmas is delivering cards to houses numbered 1 to 100.  The price for each card is the same as the house number so, for example, house number 9 requires 9p in stamps, house number 38 needs 38p worth of stamps and of course, house number 39 needs 39p.

Unfortunately, his elves have run out of all the stamps except for 3p and 5p.

Which houses can Father Christmas not get a letter to?

Got an answer? Please leave a comment below.

Mr Pitts currently teaches Computing to the whole school along with some other subjects during teacher’s PPA time. He runs this website and makes sure it all works smoothly, most of the time!