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Visualizing equivalent fractions

Sal uses fraction models to show equivalent fractions. Created by Sal Khan.

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  • female robot amelia style avatar for user SummerFire
    I keep getting confused over what a denominator and a numerator is😟
    (28 votes)
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    • starky ultimate style avatar for user Patrick Shanahan
      Have you heard of a "denomination"? People don't use this word much anymore, but when we paid with cash all the time, it was a common word. The denomination of a paper bill is, for example, a "twenty". The denomination of a coin is, for example, 25 cents. to describe a collection of money, we must use two numbers, not one. For example, I have 2 twenties. the two, is the count, or the "numerator". In the world of fractions, this means that if I have a bag with 1/4 (quarters), if I want to label the bag, I have to use 2 numbers, somewhere I need to write quarter, and somewhere I have to write how many quarters are in the bag. So we have all agreed (about 1,500 years ago) to label a bag with three quarters, 3/4. The count goes on the top (or on the left) and the denomination, the number of pieces the whole was cut into (the denominator) goes on the bottom (or the right).
      (21 votes)
  • male robot hal style avatar for user daims
    i dont get it please help
    (5 votes)
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  • aqualine ultimate style avatar for user KIMMY COLEMAN-ROBINSON
    i still don't get this can u make another video for dumb people like me
    (4 votes)
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  • blobby green style avatar for user coolbeans2467
    After being elected as president of the Constitutional Convention, George Washington thought his service to his country was over. The country had other plans. Washington was voted unanimously to be the first president of the new democratic republic. As the first president, he knew his actions would set an example for all who followed. Washington worked hard to set an example of fairness, wisdom, and honesty.

    Washington would not let the office of the president run like a royal court. He wore plain suits and refused to act like royalty. He asked to be called “Mr. President” and not superior titles like “His Excellency” or “His Highness, the Protector of Our Liberties.” These titles were how a monarch was addressed. Washington did not want to be a monarch. He set regular hours to work on government business and meet with the members of his Cabinet. He appointed his former general Henry Knox to be secretary of war, Thomas Jefferson as secretary of state, Alexander Hamilton as secretary of the treasury, and Edmund Randolph as attorney general. These men were critical in setting the course of government.

    After serving two terms (eight years) as president, Washington stepped away from government leadership. He had previously resigned his military commission as general of the Continental Army. During his resignation speech, he gave advice for the future. “Observe good faith and justice towards all nations; cultivate peace and harmony with all.”
    Washington retired to his home on Mount Vernon in Virginia. He accepted the honor of the new capital, Washington, D.C., being named for him. He then enjoyed the business of his plantation. He died in December 1799. The nation mourned the man, the general, and the president. A friend, Henry Lee, captured the feelings of the country when he said: “Washington was first in peace, first in war, and first in the hearts of his countrymen.”
    (3 votes)
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  • blobby green style avatar for user Heaven
    What is one thing that kids most likely 6th graders always have trouble with. Or might need help with
    (3 votes)
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  • stelly orange style avatar for user 4043545
    how do we even do this, i don't understand the question...
    (3 votes)
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  • purple pi purple style avatar for user Tamyra2Fobbs
    can you add fractiones if the dominater is diffrent in 4 grade
    (1 vote)
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  • duskpin tree style avatar for user maya
    how do you get a equivalent fraction
    (0 votes)
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  • piceratops ultimate style avatar for user bboycdx
    You can also divided the fraction both if it divisble by a number.
    (2 votes)
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  • blobby green style avatar for user AJJ
    this video was really helpful. thank you for the education you have given me, Sal Khan.
    (2 votes)
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Video transcript

Let's think about what fraction of this grid is actually shaded in pink. So the first thing we want to think about is how many equal sections do we have here? Well, this is a 1, 2, 3, 4, 5 by 1, 2, 3 grid. So there's 15 sections here. You could also count it-- 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15. So there are 15 equal sections here. And how many of those equal sections are actually shaded in this kind of pinkish color? Well, We have 1, 2, 3, 4, 5, 6. So it's 6/15 is shaded in. But I want to simplify this more. I have a feeling that there's some equivalent fractions that represent the exact same thing as 6/15. And to get a sense of that, let me redraw this a little bit, where I still shade in six of these rectangles, but I'll shade them a little bit in one chunk. So let me throw in another grid right over here, and let me attempt to shade in the rectangles as fast as possible. So that is 1-- 1 rectangle. I'll even make my thing even bigger. All right, 1 rectangle, 2 rectangles, 3 rectangles-- halfway there-- 4 rectangles, 5 rectangles shaded in and now 6 rectangles shaded in. So this right over here, what I just did, this is still 6 rectangles of the 15 rectangles are shaded in. So this is still 6/15. These are representing the same thing. But how can I simplify this even more? Well, when you look at it numerically, you see that both 6 and 15 are divisible by 3. In fact, their greatest common factor is 3. So what happens if we divide the numerator and denominator by 3? If we do the same thing to the numerator and the denominator, we're not going to be changing the value of the fraction. So let's divide the numerator by 3 and divide the denominator by 3. And what do we get? We get 2 over 5. Now how does this make sense in the context of this diagram right here? Well, we started off with 6 shaded in. You divide by 3, you have 2 shaded in. So you're essentially saying, hey, let's group these into sections of 3. So let's say that this right over here is one section of 3. This is one section of 3 right over here. So that's one section of 3. And then this is another section of 3 right over here. And so you have two sections of 3. And actually let me color it in a little bit better. So you have two sections of 3. And if you were to combine them, it looks just like this. Notice this is covering the exact same area as your 6 smaller ones did. And then how many equal sections of this size do you have on this entire thing? Well, you have 5 equal sections. Because this is one section of 3 right over here, this is another section of 3. And then this is another section of 3. So notice, you're covering the exact same area of the original thing. You're covering 2 out of the 5 equal sections. So 2/5 and 6/15 are equivalent fractions. So if you want to say what fraction of this is covered in the simplest form, you would say 2/5.