C.P of the total land=Rs.3,00,000
Sold 13rd of land at the loss of 20%
C.P of 13rd of land=13×3,00,000=Rs1,00,000
S.P of 13rd of land=C.P×(1−loss%100)
=1,00,000×(1−20100)=1,00,000×80100=Rs.80,000
Similarly, sold 25th at a gain of 25% is
C.P of 25th of land=25×3,00,000=Rs.1,20,000
S.P of 25th of land=1,20,000×(1+25100)
=1,20,000×125100=Rs1,50,000
Total Gain% required=10%
Total S.P required=Total C.P×(1+Gain%100)
=3,00,000×(1+10100)=3,60,000×110100=Rs.3,30,000
S.P of balance land=3,30,000−80,000−1,50,000=Rs.1,00,000
∴ he has to sell the balance land at Rs.1,00,000