1000 soldiers in a fort had enough food provision for 20 days. But some soldiers were transferred to another fort and the same food provision lasted for 25 days. How many soldiers were transferred?

200

For 20 days fort has food for 1000 soldiers

For 1 days fort has food for 1000×20 soldiers

For 25 days fort has food for 1000×20/25 soldiers = 800 soldiers

1000 − 800=200 soldiers were transferred.