Divide then join something back together. When you join it back together, it won't be whole again, but you can see the two parts you divided apart. You can also compare them and see which is bigger and by how much. You can easily find the ratio this way, too.
This word uses the kun'yomi readings for both kanji. You've learned them both already, so you should be able to read this already!
In Japan, noodles that contain one hundred percent buckwheat flour are called Juwari-soba.