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Multiplying decimals word problem

Video transcript
What is the cost of 14.6 gallons of gasoline at $2.70 per gallon? So we have 14.6 gallons, and each gallon's going to cost $2.70. Or we can even view $2.70 as 2.7 dollars. Let's just multiply times 2.7. It makes things a little bit simpler. I think you'll appreciate $2.70 is the same thing as 2.7 dollars per gallon. So let's multiply this out. So first we have, and just as a reminder, when you multiply decimals, you just have to treat the numbers like whole numbers and then worry about the decimals later. So right now, we can just view this as 146 times 27, and then we'll worry about the decimals. So first we have a 7 times a 6. 7 times 6 is 42. Regroup the 4. 7 times 4 is 28, plus 4 is 32. Regroup the 3. 7 times 1 is 7, plus 3 is 10. So we get 7 times 146 is 1,022. Now we're going to deal with this 2. But this 2, at least before we consider the decimal, is really a 20. So we're going to put a 0 here. We're doing it exactly the same way we do a traditional multiplication problem. We're ignoring the decimals for now. 2 times 6 is 12. Carry the 1, or regroup the 1. We can ignore these guys right now. 2 times 4 is 8, plus 1 is 9. 2 times 1 is 2, and now we can add. And we get 2 plus 0 is 2. 2 plus 2 is 4. 0 plus 9 is 9. 1 plus 2 is 3. Now we've figured out what 146 times 27 is. It's 3,942. But this wasn't 146 times 27. It was 14.6 times 2.7. So now we have to worry about the decimals. We just count how many numbers are sitting behind decimals. We have one right there and a second one right there. So our product has to have two numbers to the right of the decimal. So one, two, stick it right over there. So for 14.6 gallons of gas at $2.70 per gallon, it's going to cost $39.42.