Can 60hz transformer be operated at 50hz how?

As per transformer equation,E=4.44 * freq * flux * Turns.So

E/ freq =Flux.

So when a transformer is designed for 60Hz ,it CANNOT be operated at 50Hz and if operated may create heating effects and core saturation etc.

Because E/60< E/50.

However the converse condition is true i.e. a 50 HZ transformer can be used for 60Hz application

Because E/50>E/60