\frac{Ob_{A'B'C'D'}}{Ob_{ABCD}}=k
BC = x
\frac{48}{2*5+2*x}=3
\frac{48}{10+2x}=3
3(10+2x)=48 |:3
10+2x=16
2x=16-10
2x=6 |:2
x=3[cm]
BC = 3 cm <–odpowiedź
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sprawdzenie:
\frac{Ob_{A'B'C'D'}}{Ob_{ABCD}}=k
\frac{48}{2*5+2*3}=\frac{48}{16}=3