Multiplying with decimals can be tricky, but it doesn't have to be. What I like to do is just forget the decimals until the end of the problem. all you have to do is count the numbers on the right side of the decimals. 4.15 has two numbers on the right side of the decimal and 6.3 has 1 number on the right side of the decimal, so all together we have 3 numbers on the right side of the decimals. We'll remember that later. For now, we'll just multiply:
5 5 x 3 = 15, leave the one down and carry the 1 (or ten)
45 3 x 1 = 3 plus the carried 1 =4
1245 3 x 4 = 12
X X is our placeholder
0X 6 x 5 = 30, leave the 0 down and carry the 3 (or thirty)
90X 6 x 1 = 6 plus the carried 3 = 9
2490X 6 x 4 = 24
Now we have to remember how many numbers were to the right of the decimal in the original problem. It was three. So, s=we take our solution, 26145, and count from the right, three numbers and place the decimal there.
26.145 is the solution
Hope this helps!