Let's roll up our sleeves and solve this. We have 729 and we're going to multiply it by 4, essentially adding 729 to itself 4 times.
Step 1: 0 + 729 = 729
Step 2: 729 + 729 = 1458
Step 3: 1458 + 729 = 2187
Step 4: 2187 + 729 = 2916

So, 729*4 = 2916