Problem number 7. Each digit shown on the right is made using a piece of ribbon. Which piece of ribbon is the longest? 1, 2, 5, 6, or they are all the same length? When we look at the way the numbers are made, we see that the ribbons are folded over on some of the squares. Let's think about folding a ribbon and see what it means for how long it is. Here's a video of a ribbon where we will fold over a corner. We can see that there is a double thickness of ribbon on the fold. That means that where we have triangles here instead of full squares filled in, we can still count it as a full square because it's doubled. So, let's just count. For the digit 1, we have 1, 2, 3, 4, 5, 6 for the length. For the digit 2, we have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 for the length. You might notice that the digit 5 is just a mirror image of the digit 2. Let's count it anyways. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. Now, let's look at the length of the ribbon used to make the digit 6. 1, 2, 3, 4, 5. Here the ribbon goes under another piece. 6, 7, 8, 9, 10, 11, 12, and 13 because there is two pieces of ribbon on that one square. So, the digit 6 is made up of 13 units of length. So, the answer is D. The piece of ribbon that makes the 6 is the longest.

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