7. x,y,z d.p cu 15, 28 si 40 ⇒ conform definitiei ca
[tex] \frac{x}{15} = \frac{y}{28} = \frac{z}{40} =k[/tex]
x=15k, y=28k, z=40k
x+y+z= 249
15k+28k+40k=249
83k =249
k= 3
adica x=15*3=45, y=28*3=84, z=40*3=120
8. La fel obtii ca a,b,c d.p cu 5,12,13
a+b+c=90 cm
a=5k,b=12k.c=13k
5k+12k+13k=30k=90 cm ⇒ k=3
a=3*5=15cm, b=12*3=36 cm, c=13*3=39 cm
20. x=2,4K, y=1,8k, z=1,7k
2,4k+1,8k+1,7k=5,9 k
5,9k- 3/4*5,9k= 59l
Impart prin 5.9
k-3k/4=10
4k-3k=40
k=40
x=96
y=72
z=68
