segmentele proportionale le voi nota cu a, b,c
a/12=b/15=c/20=k
a/12=k=>a=12k
b/15=k=>b=15k
c/20=k=>c=20k
a+b+c=47mc
dar 47 cm=470mm
deci a+b+c=470
12k+15l+20k=470
47k=470
k=740:47=>k=10
daca k=10=>a=10 ori 10=>a=120mm
b=15 ori10=> b=150mm
c=20 ori 10=> c=200mm
