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Ratio word problem: boys to girls | Pre-Algebra | Khan Academy

Ratio word problem: boys to girls | Pre-Algebra | Khan Academy


In a language class, the girl to boy ratio is 5 to 8. So for every 5 girls, we have 8 boys. If there are a total of 65 students, how many girls are there? So this is interesting. They give us the ratio of girls to boys. But then they want us to think about how many girls there are given that there are 65 total students. So what we really want to think about is not just the ratio of girls to boys – we want to think about the ratio of girls to total students. So how can we figure out what this ratio’s going to be? Well the girl-to-boy ratio gives us a good clue. If there are 5 girls for every 8 boys, how many total students are there going to be for every 5 girls? Well for every 5 girls, you’re going to have 5 girls and 8 boys. You’re going to have 13 total students. So I just added the 5 and the 8 right over here. The ratio of girls to total students is 5 to 13. One way of thinking about it is if you were to evenly divide the students into groups of 13, every group of 13 students would have 5 girls. Now, I think we’re ready to figure out how many total girls there are. Because they tell us that there are 65 students. So, we don’t just have one group of 13, we have 65 students. And how many groups of 13 are in 65? Well to go from 13 to 65, you have to multiply by 5. 5 × 10 is 50 and 5 × 3 is 15. Right. So, 13 × 5 is 65. So essentially, one way you could view it is you have 5 groups of 13. So if you have 5 groups of 13, each of those are going to have 5 girls. Multiply by 5, and you’re going to have 25 girls. So for every 65 students, you’re going to have 25 girls, given the information that has been given.

Comments (43)

  1. Excellent. Succinct. I seriously wasted time in school. Fuck school. Sending my future kids to Khan's esteemed Academy. Located online.

  2. O.o

    Or just 5/13 x 65 = 25?? Same answer, yet a little shorter.

  3. Or 5x+8x=65 solve for x which is 5 and then do 5×5

  4. how about if it does not go into it

  5. Khan Academy- You make math understandable – You are my "math crush"

  6. Also I  cannot find this  video on  the educational Khan Academy site-even when  I use this title – hope you upload it there – your  a great resource

  7. My teacher showed the class this video and she told us to go to it this was so understandable!

  8. Thanks for the video it very helpful

  9. Thank you for the video

  10. does khan academy answer questions on youtube?

  11. Thanks for the sharing and simple learning thank you!

  12. that was very helpful

  13. This help me so much thank you for helping me?✏️?

  14. yup im gonna fail math

  15. Can anyone help me out with this problem———In a photo,the constant of proportionality is 3 over 4 inch of height for every inch of width.The actual height of the image is 15 feet.What is the actual width of the image?

  16. Please tell me how this is pre-algebra ? This is just a 4th grade ratio problem

  17. Teacher its just i dont know what ratio means

  18. Thank u so much I have a spring break packet and this helped me so much I appreciate it thank uuuu

  19. I wish my teacher could explain in such a way

  20. this is the worst vid i can not se any thing

  21. Thank you sir I have a test tomorrow

  22. Thankyou,because it tought me lots of things..Actually Im dumb at math but because of this video it helped me a lot..Continue making videos I inspired

  23. I have a benchmark test for 6th grade tomorrow thx so much !!

  24. Please make videos cce pattern math

  25. I low key watch this when I don’t need to

  26. This is important topic by doing it in 2:04 sec it is rather confusing as I see this formula would not work in all condition what if total number of students is not given?

  27. Guys my dad Said if I don’t answer his questions correctly he won’t bring me to the movie

  28. My teacher doesn’t teach like this thank you.

  29. WHAT ABOUT 8/5= 1.6 : 1 and 65/1.6 gets 40 those are boys and the left one's are girls

  30. How do you compare ratio? If one ratio is bigger than the other what is it significance? I hope you understand the question.

  31. How does he Wright that good with a mouse

  32. And who goes to Bryant

  33. For the second time i have started ratio but i did not understand anything now i have understod every yummy piece of maths

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