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September 25th, 2018, 09:47 PM   #1
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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.
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September 25th, 2018, 10:43 PM   #2
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September 25th, 2018, 11:12 PM   #3
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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.
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September 26th, 2018, 06:50 AM   #4
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Yes.
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June 25th, 2019, 03:37 PM   #5
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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.
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June 25th, 2019, 07:12 PM   #6
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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.
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June 27th, 2019, 11:40 AM   #7
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Quote:
Originally Posted by BRYTBRTRTBRTY View Post
… 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!

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