Two circles have diameters in the ratio 1:3. Find the ratio of their circumferences.

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- December 21st 2009, 12:31 AMumageometry
Two circles have diameters in the ratio 1:3. Find the ratio of their circumferences.

- December 21st 2009, 01:53 AMGrandad
Hello umaThe ratio of

*any*two corresponding lengths of two similar figures will be the same, no matter which two corresponding lengths are chosen. So if the diameters are in the ratio 1:3, the circumferences will also be in the ratio 1:3.

(Note, though, that the areas will be in the*square*of this ratio; so they'll be in the ratio 1:9.)

Grandad - December 21st 2009, 03:18 AMmathaddict