OK, let's work through this together. We're starting with 635 and we're going to multiply it by 4, which means we add 635 to itself 4 times.
Step 1: 0 + 635 = 635
Step 2: 635 + 635 = 1270
Step 3: 1270 + 635 = 1905
Step 4: 1905 + 635 = 2540

So, 635*4 = 2540