Multiplying decimal appears to be harder than it actually is. When you are multiplying decimals, you can “ignore” the decimals and just multiply the numbers the way it is. After you’ve multiplied and added your numbers, then count the numbers after the decimal in the original problem and then apply that to your answer.
12.345 X 67.89
In the number 12.345, there are 3 numbers after the decimal.
In the number 67.89, there are 2 numbers after the decimal.
Adding 2 + 3, your final answers will have 5 numbers after the decimal.
You can do the problem like this: (writing it without the decimals)
12345 X 6789 = 83810205
You know that your final answers will have 5 numbers after the decimal, so you count 5 numbers backward starting with 5, 0, 2, 0, 1 you got your five numbers. Put your decimal in front of the number 1.