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Lesson 4: Dividing fractions and whole numbers

# Dividing a fraction by a whole number

Dividing fractions by whole numbers can be done visually or using multiplication. To find the result of 2/3 divided by 5, divide 2/3 into 5 equal parts, each representing 2/15 of the whole. Alternatively, multiply 2/3 by 1/5, resulting in 2/15 as the final answer.

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• So... Denominator times whole number = New denominator...
And the numerator stays the same?

If this makes sense, please vote up!
• If you look up " keep change flip" It is an awesome method. He is showing it here, but the visual made it kind of confusing for me. Hope this helps!
• If anyone is confused, think of it like this:
1. KEEP: the first number stays the same.
2. CHANGE: turn division into multiplication
3. FLIP: All whole numbers have an invisible one and a fraction bar over them. Flip it so the one is on the bottom and your original number is on the top. For fractions, the denominator and the numerator flip
You just multiply like normal.
• So.. dividing and multiplying fractions are the same?
• Not quite. Dividing requires the extra step of inverting the second fraction, before multiplying the fractions.

Have a blessed, wonderful day!
• Sorry sal, but dosent make sense to me! please help me understand this in an easier way :(
• The idea comes from dividing fractions.
There are three possibilities, fraction divided by fraction such as (4/5)/(16/15) where you flip the denominator and multiply to get (4/5)(15/16) which will reduce to 3/4.
The other two have a whole number in numerator or denominator. In this case, you can change whole number to a fraction by dividing by 1.
Examples: (5)/(20/4) = (5/1)/(20/4) = (5/1)(4/20) = 1
(20/3)/5=(20/3)/(5/1)=(20/3)(1/5)=4/3.
Converting a whole number to a fraction by dividing by 1 is important in math in Algebra for slope and other applications.
• why overcomplicate it by making the whole number into a fraction when you can just flip the fraction allowing you to multiply? Or is that not how this works?
• This doesn’t work because the numerator and denominator would be reversed in the answer.

For example, 3/4 divided by 8 is 3/4 x 1/8 = 3/32. Note that 4/3 x 8 would instead give 32/3.

Have a blessed, wonderful day!
• If Sal had not divided had not divided all the thirds into 5 equal sections at would he have gotten the answer wrong ?
• No he wouldn’t
• For those who are still confused, let me try explaining.
Let's use the same numbers, 2/3 divided by 5. We use this method called "keep, change flip" at our school, which is how Sal did it as well. Basically, you keep the 2/3 the same, you change the division sign into a multiplication sign, and turn 5 into the fraction 5/1, but flip it to be 1/5. Then multiply! 2 x 1 is 2, and 5 x 3 is 15, so you get 2/15. Hope that helped!