Maths Puzzle

[sbrown1450]

I have 3 beakers.
One holds 10 cups
The second holds 7 cups
The third hold 3 cups.
I need 5 cups.
How do I do it?
Thanks. You

[Baldric]

https://www.chaptercheats.com/qna/iphone-ipod/125437/Hidden-Artifact-Agency-Answers.htm?qid=106050

[Tilly2]

Half fill the 10 cup one. :-)

[bhg481]

fill the 7, pour it into the 3, then throw it away.
Repeat. The 7 now holds 1 cup - pour it into the 10.
Fill the 7, pour it into the 3, leaves 4 in the 7.
Add the contents of the 7 to the 10.

[Tilly2]

....or half fill the 10 cup. :-)

[fiction-factory]

Depending on the shape of the cup, that might not be easy to do with sufficient accuracy, Tilly

[Tilly2]

I know, FF :-)

...but beakers tend to be straight sided, don't they?

[fiction-factory]

Without further information we can't assume it's cylidrical though- it could be a truncated cone shape. We also can't assume we have a ruler. The bhg solution doesn't make these assumptions. Having said that, the solution does assume an adequate supply of liquid is available

[sbrown1450]

Beakers are cylindrical. Cannot empty them out.

[bhg481]

Fill the 3, pour it into the 7
repeat
repeat until 7 is full, leaves 2 in the 3.
Pour this into the ten.
fill 3 again and pour into 10.
10 now contains 2 + 3 = 5.

[fiction-factory]

But for some reason sbrown now says the beakers can' be emptied out, bhg.

[bhg481]

FF - I assume that meant "thrown away".

[Tilly2]

Can't be emptied out?

[sbrown1450]

Still have no answer?

[fiction-factory]

Do you mean in addition to the answers given above?

[Mamyalynne]

I think you threw people when you stated the beakers can't be emptied out - do you mean you cannot pour from one to the other as offered in the solutions above?

[elliemay1]

sbrown, did you read the solutions on Baldric's link @16.41 on Friday?

[Togo]

Fill 10 cup
fill 3 cup from 10 cup
pour 3 cup into 7 cup
fill 3 cup from remainder of 10 cup
again pour 3 cup into 7 cup
fill 3 cup again (this leaves 1 cup in 10 cup)
pour from 3 cup to fill 7 cup( this leaves 2 cups in 3 cup. 1 cup in 10 cup and 7 cup full)
pour 7 cup into 10 cup beaker( leaving 7 cup empty 10 cup holding 8 cups and 3 cup holding 2 cups)
pour 2 cups from 3 cup into 7 cup
fill 3 cup from 10 cup leaving 5 cups in 10 cup, 3 cup full, and 7 cup holding 2 cups.