Question

Suma a 3 numere este 90, aflati numerele stiind ca sunt direct proportionale cu 5, 12, 13.+

Answer 1

x/5=y/12=z/13 = (x+y+z)/(5+12+13)=90/30 = 3

x=5*3=15  ;  y=12*3=36  si  z=13*3=39  ;

Answer 2

a+b+c = 90
a/5=b/12=c/13
a/5 = b/12 =>12a= 5b => b = 12a/5
a/5=c/13 =>13a = 5c => c = 13a/5
inlocuim in prima ecuatie pe b si pe c
a+12a/5+13a/5 = 90 |×5
5a+12a+13a = 450
30a = 450
a = 450:30
a = 15
b = 12a/5 = 12×15/5 = 12×3 = 36
c = 13a/5 = 13×15/5 = 13×3 = 39

Verificare:
15+36+39 = 90

Numerele sunt: 15; 36; 39.