1. a + b + c =40
0,2a = 0,5b = 1/3 ·c
b = 0,2÷0,5·a = 0,4a c = 0,2·3a = 0,6a
a+0,4a +0,6a =40
2a = 40 a = 20 , b= 8 , c = 12
2.
Fie x,y si z cele 3 parti invers proportionale rezulta x*2=y*5=z*6
[2,5,6]=30
x*2=y*5=z*6 |:30 rezulta x/15=y/6=z/5=(x+y+z)/(15+6+5)=56/26
3.a+b+c=220
0,2= 2/10=1/5
0,5=5/10=1/2
0,25=25/100=1/4
a,b,c ip 1/5 1/2 1/4
a*1/5= b* 1/2 =c * 1/4=k
a/5= b/2= c/4=k
a=5k
b=2k
c=4k
5k+2k+ 4k= 220
11k=220
k=20
a=100
b=40
C=80
4.
Fie x,y si z cele 3 parti invers proportionale rezulta x*2=y*5=z*6
[2,5,6]=30
x*2=y*5=z*6 |:30 rezulta x/15=y/6=z/5=(x+y+z)/(15+6+5)=95/26