Question 539383
<pre>
To divide a number in N into three parts in the ratio of a:b:c

first part = {{{a/(a+b+c)}}}×N
second part = {{{b/(a+b+c)}}}×N
third part = {{{c/(a+b+c)}}}×N

To divide a perimeter 60 into three sides in the ratio of 3:4:5

first side = {{{3/(3+4+5)}}}×60 = {{{3/12}}}×60 = {{{1/4}}}×60 = 15
second side = {{{4/(3+4+5)}}}×60 = {{{4/12}}}×60 = {{{1/3}}}×60 = 20 
third side = {{{5/(3+4+5)}}}×60 = {{{5/12}}}×60 = 25

Edwin</pre>