The ratio of coefficients of HNO3,Fe(NO3)2  and NH4NO3  in the  redox equation Fe+HNO3→Fe(NO3)2+NH4NO3+H2O in the balanced from will be

Fe0+HNO3+5→Fe+2(NO3)2+NH4−3NO2+H2O (i) Fe0→Fe+2(NO3)2↓2 (ii)HNO3+5→NH4−3NO3↓8 To make increase in O.N.=decrease, multiply eqn.(i) by 4 and add. Hence4Fe+HNO3→4Fe(NO3)2+NH4NO3 To balance N atoms on the two sides, multiply HNO3  by 10. Hence4Fe+10HNO3→4Fe(NO3)2+NH4NO3 To balance O-atoms, add 3H2O  on RHS. Hence 4Fe+10HNO3→                           4Fe(NO3)2+NH4NO3+3H2O H atoms are automatically balanced.