# Knapsack Problem using Greedy Algorithm

I am required to show that using the obvious greedy algorithm (which I'm assuming is the approach of choosing the highest value-by-weight items first) to solve the Knapsack problem yields a result that is greater than half of the optimal value. I'm unsure about how to go about solving this. Any help would be appreciated. Also, the question mentions using the "obvious" greedy algorithm which I assume is what I described in the parentheses above. Is this a correct assumption to make?