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Lesson 3: Multiplying decimals

# Developing strategies for multiplying 2-digit decimals

Learn to multiply decimals by treating them as fractions. Practice converting decimals to fractions and then multiplying like usual. Then convert the fractions back to decimals to solve!

## Want to join the conversation?

• Is there an easier way to do this? I mean, what if you don't have a piece of paper and can't write that well on the computer? Is there some way you could do this in your head?
• How do you multiply a big whole number, like 217 with a long decimal like 19.45? I've looked for a while for a video on that, but can't find one. I'm guessing you just do what Sal said but don't count any places over the decimal. But I'm not sure so please respond.
• One way we can multiply those numbers or digits is area model or standard
• Can't you just use the standard algorithm for this or just multiply them without decimals and add the m later on.
• Yes, you could, but the will lower you concept of you understanding how multiplying with decimals work. Try learning the right way first then using any tricks.
• What is 0.24 x 0.0009897 ? How do U solve that?
• You multiply 24 times 9897 and then you move the decimal 9 places to the left.
• can you do a problem like 0.08 times 0.38
• Yes, you can.
EX:
0.08
x 0.38
------ You would do the regular standard algorithm then count how many digits
that are to the right to the right of the decimal points. That is how many digits are after you decimal point. So you count from the right of your answer the amount of digits that are after the decimal point and that is where you put your decimal point.
• how do you do it when the first digit in the number is 0?
• what do u mean by 3 1/10?
• three is the whole number and 1/10 is the fraction.
its a mixed number.
• Example: 3.14 x 2.5. SO first thing to do is to line them up like regular multiplacation.

Do all the math, and dont place the decimal point yet. So you get the answer of 7850. So, in the equation, you looke at the factors. 3.14 has 2 decimal places, and 2.5 has 1. So 2+1=3, so start at the farthest to the right decimal value, and do three jumps between the numbers, or just go 3 numbers in from the smallest decimal value. If you did everything correctly, the answer is 7.850, or 7.85.