Question 1183921
a:b=2:5 and a:c=3:7. What is c:b?
<pre>
Product of the means equals the product of the extremes:

5a = 2b and 7a = 3c

{{{system(5a=2b,7a=3c)}}}

Dividing equals by equals:

{{{(5a)/(7a)=(2b)/(3c)}}}

{{{(5cross(a))/(7cross(a))=(2b)/(3c)}}}

{{{5/7=(2b)/(3c)}}}

Cross-multiply:

{{{15c=14b}}}

{{{c*15=b*14}}} Make c and 15 the extremes, and 14 and b the means:

{{{c:b=14:15}}}

Edwin</pre>