SOLUTION: My son brought home a math problem from his 5th grade math class. There is no explanation on the page and he claims he's never seen it before. The problem is as follows--->

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Question 29848: My son brought home a math problem from his 5th grade math class. There is no explanation on the page and he claims he's never seen it before. The problem is as follows---> 3:15::60:_____
I have searched to understand what the colons and double-colon signify but cannot locate the use. Is this to infer a sequence that he is supposed to finish? If so, what is the significance between the single and double colon.
Found 2 solutions by Cintchr, longjonsilver:
Answer by Cintchr(481) About Me  (Show Source):
You can put this solution on YOUR website!
3:15::60:_____
: is to
:: as
this is an analogy, like finger:hand::toe:foot
it shows a comparison. A better way to write this ...
: is /
:: is =
+3%2F15+=+60%2Fx+ you are finding equivalent fractions :)
since 3*20 = 60
then 15 * 20 = x
300 = x

Answer by longjonsilver(2297) About Me  (Show Source):
You can put this solution on YOUR website!
the : symbol is used in ratios.

if i have $30 and you have $50, we can say the ratio is 30:50 or 3:5.

The double colon i have not seen but i am guessing it is saying:

you have the ratio 3:15 and also the ratio 60:x and these ratios are the same.

Method:
3:15 scaled up by factor of 20 is 60:300

so the unknown is, i believe, 300

Jon.