Bill put his french fries in the oven after it finished heating. The recommended time was 5 minutes for them to be fully cooked. He put them in for 45 seconds. How many seconds remained? Let's answer step by step:
Each minute last 60 seconds, so that means for the fries to be fully cooked Bill needs to cook them for 5 * 60 = 300 seconds. Since Bill had the fries in the oven for 45 seconds so far, that means they need to stay in the oven for another 300 - 45 = 255 seconds. The answer: 255.