Question

Cosmin a colectionat 27 de timbre mari si mici pt a platit 142,80 lei.Cate timbre mari si cate timbre mici a cumparat daca un timbru mare costa 7,60 lei iar unul mic costa 2,40 lei?

Answer 1

a=nr. timbre mari
b=nr. timbre mici
a+b=27
7.60 xa+2.40xb=142.80
a=27-b
7.60x(27-b)+2.40xb=142.80
205.20-7.60xb+2.40xb=142.80
(7.60-2.40)xb=205.20-142.80
5.20xb=62.40
b=62.40:5.20=12
a=27-12=15

verificare 15x7.60+12x2.40=114+28.80=142.80 ok