When the redox equation #Cr^(3+)(aq) + 3Mn(s) -> Mn^(2+)(aq) + Cr(s)# is completely balanced, what will the coefficient of #Cr^(3+)(aq)# be?
Manganese is oxidized:
Chromium is reduced:
And so we take
Charge is balanced, and mass is balanced, and so this is a reasonable representation of reality. Whether the reaction actually works, I don't know, and cannot be bothered to look up redox tables.