Răspuns:
m,impur=230kg
m,impur= m,pur+impuritati
din p=90%, deduc
100kg subst.impura...........90kg subst. pura--------10kg impuritati
230kg..........................................x......................................x
m,pura= 230x90/100kg=207kg
impuritati= 230x10/100kg= 23kg
Explicație: