You can put this solution on YOUR website!
You can do this a number of ways. I'll show you two:
First, you have 2 meters of copper tubing that weighs .25kg and you want to know how much 50 meters weighs. You may be able to see by inspection that you want to have 25 times more meters of tubing, and just multiply the weight by 25 also. So your answer would be .25 X 25 = 6.25 kg.
Secondly, if you didn't recognize that, set up a proportion:
2 meters of tubing/.25kg = 50 meters of tubing / x kg
Solve for the ratio by cross multiplying:
2x = 50 X .25, thus 2x = 12.5.
Divide both sides by 2 to solve for x and you get x = 6.25