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 Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion

 September 25th, 2018, 09:47 PM #1 Banned Camp   Joined: Sep 2018 From: tytyt Posts: 32 Thanks: 0 How to solve this Hello If the ratio of chocolates to ice-cream cones in a box is 5:8 and the number of chocolates is 30, find the number of ice-cream cones. Last edited by skipjack; June 25th, 2019 at 03:52 PM. September 25th, 2018, 10:43 PM #2 Senior Member   Joined: Sep 2015 From: USA Posts: 2,530 Thanks: 1390 what is your problem? September 25th, 2018, 11:12 PM #3 Banned Camp   Joined: Sep 2018 From: tytyt Posts: 32 Thanks: 0 Hello The chocolates to ice-cream cones ratio is 5:8=chocolates:ice-cream cones 5/8=30/ice-cream cones ice-cream cones = 30*8/5 ice-cream cones = 240/5 ice-cream cones will be 48; is this right/correct? Last edited by skipjack; June 25th, 2019 at 03:54 PM. September 26th, 2018, 06:50 AM #4 Global Moderator   Joined: Dec 2006 Posts: 20,926 Thanks: 2205 Yes. June 25th, 2019, 03:37 PM #5 Newbie   Joined: Jun 2019 From: New York Posts: 23 Thanks: 0 Hello I got 48 as well. By placing 5/30= 8/x, cross multiplying it will be 5x=240.Then x= 240/5, which is equal to 48. 48 Ice cream cones to 30 chocolates. I saw these 2 links, that was helpful for me in solving this problem: 1) https://mathbitsnotebook.com/Geometr...y/SMRatio.html 2) Hope this helps, I agree with you it is 48. June 25th, 2019, 07:12 PM #6 Senior Member   Joined: Jan 2014 From: The backwoods of Northern Ontario Posts: 391 Thanks: 70 5:8 = 30:C Here's the way I taught my elementary pupils to solve it when I was a teacher: What do you have to multiply 5 by in order to get 30? Yes, 6 is correct. Then you also have to multiply 8 by 6 as well. That will give you the value of C. June 27th, 2019, 11:40 AM   #7
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Quote:
 Originally Posted by BRYTBRTRTBRTY … 5/8 = 30/ice-cream cones ice-cream cones = 30*8/5 … is this right …
Hello BRYT…

That's how I learned it (before algebra). The teacher described that method as "multiply on the diagonal and divide by the number not used".

$$\dfrac{5}{8} = \dfrac{30}{x}$$

The numbers 8 and 30 lie on the diagonal, so we multiply them. The number not used is 5, so we divide 8×30 by 5, just like you did.

This method works whenever you know three out of the four numbers in a proportion. Here are some symbolic examples:

$$\dfrac{A}{B} = \dfrac{C}{D}$$

If we know numbers {A,C,D}, then we get B by multiplying on the diagonal and dividing by the number not used. A & D lie on the diagonal, so C is the number not used:

B = (A×D)/C

If we know {B,C,D}, then we get A = (B×C)/D

If we know {A,B,D}, then we get C = (A×D)/B

If we know {A,B,C}, then we get D = (B×C)/A

That last example is what you did above. Cheers!  Tags solve Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post gen_shao Algebra 12 November 2nd, 2014 06:11 AM

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