Question

Intr-o cutie sunt bile rosii,albe si negre.Din total3/6 sunt bile rosaii,5/8 din rest sunt bile sunt albe,iar 9 sunt negre.Cate bile sunt in cutie?

Answer 1

r+a+n=S , 3/6×S=1/2×S=r , 5/8 (S-1/2×S)=a , n=9 deci a=5/8×1/2× S=5/16×S, 1/2×S+5/16×S+9 deci 144=16×S-13×S=3×S, S=48, r=1/2×48=24,a=5/16×48=15, n=9