Question

Numerele a,b si c sunt direct proportionale cu 4,5,respectiv 7.Aflati numerele a,b si c stiind ca 3a+c=285

Answer 1

{a,b,c} dp {4,5,7}
a/4=b/5=c/7=k
=>>a=4k
b=5k
c=7k
3a+c=285
3•4k+7k=285
12+7k=285
19k=285 |:19
k=15
Aflam pe a ,b, c:
a=4k=4•15=60
b=5k=5•15=75
c=7k=7•15=105
Succes!

Answer 2

a/4=b/5=c/7 =k
a/4 =k  ;   a =4k
b/5 =k  ;   b =5k
c/7 =k  ;   c =7k

3a+c =285
3*4k+7k =285
12k+7k=285
19k =285
k =15

a=4k =4*15 =60
b=5k =5*15 =75
c=7k =7*15=105
v ;  3*60+105 =180+105=285