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# Strategies for multiplying decimals and whole numbers

We can use different methods for multiplying whole numbers with decimals. The first method involves converting the decimal into a fraction and multiplying the numerators and denominators together. The second method involves breaking the decimal into different place values and multiplying each part by the whole number. Estimating the answer beforehand can help check for accuracy. Created by Sal Khan.

## Want to join the conversation?

• If anyone is stuck, an example is 9 x 2.0 how do you solve it put the answer in the comments.
• 18 because 2.0 is exactly the same as 2.
• Another Example is: 45 x 0.8 = first multiply your 2 numbers, ignore the zero and decimal. multiply 45 x 8= ? then put the decimal between it
• Here's an interesting thing that I learned:

Multiplication has multiple interpretations. It is not simply repeated addition.

So when we are working with say 0.8*7, we can look at it in the traditional sense that 7 times 0.8 = 0.8+0.8....+0.8 = 5.6, however practically it means 0.8 of 7 which makes more intuitive sense cos 0.8 or 80% of 7 is 5.6

Now here's the fun part- this simple understanding makes learning probability much fun:

For example, the probability of flipping two heads in a row with a fair coin is (1/2) * (1/2) = 1/4

What it simply means is the probability is 1/2 of 1/2 which is 1/4. We of course understand this to some abstract level but knowing it literally means one half of half -the wording of the problem- makes so much more sense. This fundamental understanding makes problem solving at a more complex level simpler!

Thank you team KA for making learning so much fun!
• That is a good way to think about it, and I enjoy going into Math now because I think in your way.
• For example 0.7 x 5 = 3.5 because just ignore the zero, and mutiply just the 7 and 5 then put a decimal point BOOOM! you got 35!
• Guys its not that hard, believe in yourself, one easy way is to just mutiply the whole numbers, leave the decimal, zero, or fraction, then mutiply whole numbers ONLY. add a decimal point in SIMPILIST FORM. you may need to simply if you get a larger answer that is equal
• Im having a little trouble but i get the whole concept.