Mandy works construction. She knows that a 5 meter long metal bar has a mass of 40 kg . Mandy wants to figure out the mass (w) of a bar made out of the same metal that is 3 meters long and the same thickness. What is the mass of the shorter bar?

If you take the weight and divide it by the length, you get the weight-per-meter. So, 40(kg) divided by 5(meters) gives you 8 kilograms per meter. Then to find the weight of the shorter bar, you'd multiply it's length by the number you just found. In conclusion, the shorter bar weighs 24kg.