Question

Nick wants to write

thank-you notes to 15 of
his friends. The cards
are sold in packs of 6.
How many does he need
to buy?

Answer 1

Nick needs to buy 3 packs because if he buys 2 packs he'll have 12 cards which won't be enough. He will have an extra 3 cards remaining.

Answer 2

Nick needs to buy 3 packs.

Explanation:

If Nick buys 3 packs he will have 18 cards. If he uses 15 of them he will have 3 left over. If he only bought 2 packs he would be 3 cards short of the amount he really needed.