Buy of land =480000
2/5*480000=192000 rs
loss=6%
(100-6)/100*192000=180480
total gain =12%
(100+12)/100*480000=537600
sp=537600-180480=357120
cp of remaining part of land =3/5*480000=288000
gain% of remaining part of land= sp-cp/cp*100
<=>357120-288000/288000*100
=24 %