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Numerele 7,x,y sunt invers proportionale cu numerele 15,35,21.Atunci x+y este egal cu...

Răspuns :

7×15=x×35=y×21
105=x×35
x=3
105=y×21
y=5
x+y=3+5
x+y=8
{7,x,y} i.p {15,35,21}
7×15=x×35=y×21=k
105=k
x=k/35=105/35=3
y=k/21=105/21=5
Deci: x+y=8