Solving A Proportion With An Unknown Variable (example) | 7th Grade | Khan Academy


Here’s a great video where we explain the reasoning behind solving proportions. We’ll put some algebra to work to get our answers, too.

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Grade 7th on Khan Academy: 7th grade takes much of what you learned in 6th grade to an entirely new level. In particular, you’ll now learn to do everything with negative numbers (we’re talking everything–adding, subtracting, multiplying, dividing, fractions, decimals… everything!). You’ll also take your algebraic skills to new heights by tackling two-step equations. 7th grade is also when you start thinking about probability (which is super important for realizing that casinos and lotteries are really just ways of taking money away from people who don’t know probability) and dig deeper into the world of data and statistics. Onward! (Content was selected for this grade level based on a typical curriculum in the United States.)

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18 thoughts

  1. What if the cross mutiplying result have the coeficcient as the numerator?for example we have 4/x=5/10 and the result of cross mutiplying is 5x/40?do we flip the 4/x and 5/10 so it looks like this?: x/4=10/5?

  2. I am lasagna and I eat FOOOOOODDDDDDDEDDD. this guy is stupid because f*ck ohh my god this guy is moderated

  3. For people that are confused, there is an easier way, just multiply 36 times 10 then divide by 8. the answer will still be 45

  4. This way is a way to complicated.You just have to cross multiply the numbers.Then you dived that by the other number.For example: If the problem was 8/36=10/n you multiply 36 and 10 to get 360 then you just divide it by 8 and the answer is 45.

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