A fast-food vendor sells hot dogs for one pound 50. He is also running the following deal: buy three, get one free. Sarah wants to buy the 30 members in her youth group one hot dog each. Calculate how much Sarah will need to spend.
Sarah needs 30 hot dogs. Every time she buys three, one of them is free. Imagine that each of these dots represents one of her 30 students. After the first three, she gets one for free. After the second three, another free. After the third three, a third hot dog is free. She pays for three, then gets one free. This shows that Sarah should get seven free hot dogs. How can we show this mathematically?
We can take the 30 hot dogs she needs and divide that by four, which is 7.5. We see that 0.5, that one-half here. Four goes into 30 seven times. And there’s a remainder of two. We need to round the seven and a half down and say that seven of the hot dogs will be free.
Remember, our goal is to calculate how much Sarah will need to spend. She’s buying 30 hot dogs. But seven of them she won’t have to pay for. 30 minus seven equals 23. Sarah will pay full price, one pound 50, for 23 hot dogs. 23 times 1.5 equals 34.5. And when we’re talking about money, we would say 34 pounds and 50 pence.