I made this problem-solving assignment based on an actual phone call that a customer had with his cell phone provider. The customer and the company disagree about his bill. The company quoted him .002 cents per kilobyte, but they charged him as if his rate was .002 dollars per kilobyte. The phone company contends there is no difference between .002 dollars and .002 cents, while the customer is trying to get them to understand that they are. The actual phone call can easily be found on the web by searching for the popular cell provider that starts with a V (think about it for a second because I don't want to use their name) followed by math fail. Look for a video, even though it's just an audio recording.
I like to use this when my students are learning about decimals, but I also use it to reinforce the importance of using proper units and to talk about place value. I start by giving my students the problem-solving paper that I made, and then we compare students' responses. Inevitably, their answers are split into the same two camps as the phone company and the customer - .002 dollars and .002 cents. We then share how students came up with their answer, and I end by letting them hear the actual recording.
This is a nice real-world problem-solving activity that students enjoy.