Lizzy: Tom fills a 250 pound sandbag 80% full. But the filling material he is using is 40% heavier than sand. How much does the bag weigh?.
Me: Hmmm, let me think. I think this is the detailed solution:
The bag full of sand would weigh 250 * .8 = 200 pounds. The filling material would make it 200 * .4 = 80 pounds heavier. So it weighs 200 + 80 = 280 pounds. Final answer: 280.