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# Intro to fractions

Sal divides wholes into equal-sized pieces to create unit fractions. Created by Sal Khan.

## Want to join the conversation?

• how do we simplify :

(5a)^3 divided by 5a ^-1 x 5^-2 a^2
• The first thing I like to do is multiply everything out and make all the exponents positive, just so that we can get an idea of what we're working with. You can distribute the exponents to each factor that it's raising:
125a^3 / 5^-1 * a^-1 * 5^-2 * a^2

Now that we have everything all laid out, let's make all the exponents positive, just to simplify the problem a bit more:
= 125a^3 * 5^1 * a^1 * 5^2 / a^2
= 5^3 * 5 * 5^2 * a^3 * a / a^2

Now we can combine the exponents, keeping in mind the rule for doing so:
x^a * x^b = x^(a+b)
x^a / x^b = x^(a-b)

5^(3+1+2) * a^(3+1-2)
= 5^6 * a^2

This means that the final answer is 15,625a^2
(1 vote)
• Hi, this isn't about the video, but is it possible to see a lesson about probability somewhere? I would like to know what or means in probability.
• At , why did they use the shapes a rectangle and a square?
(1 vote)
• Since both squares and rectangles have congruent (similar) sides, then they can be easily cut into integer (whole number) pieces that make it easier to understand in terms of the overall lesson.
• does the fraction have to be equal?🤔
• When you divide a shape or number into parts, the parts MUST be equal. Otherwise mathematics dosen't work.
• Go me+smart group!
• Why do fractions help us in life?
• well, fractions are very usefull. take money. i need to pay my bill of \$100 by the end of the month. i have \$35 so far. so i have 35/100 of what i need.
• Hii! um...how do you divide fractions? also i think it is very fun to multiply fractions so may u please make a video on that? Thank you!
• to multiply fractions, simply multiply the numerators, and put that over the product of the denominators. For example, lets say we have 1/5*2/3, 1(2) = 2 and 5(3) = 15, so you get 2/15, and when you divide fractions, you simply take the recipricol of the dividend and then multiply.
(1 vote)
• What is the fraction of the triangle 😕😕😕 is it 1/2