Why did God create the earth if he placed man in the garden of eden?

God created men and women to populate the earth. Adam, was placed in God's garden known as The Garden of Eden; to tend it for the Lord.

the garden of eden was placed on planet earth. you can not have te garden of eden with out the plane earth

I believe the garden of eden represents childhood innocence and bliss while the tree in the middle of the garden represents made made law - through our desire to take ourselves too seriously - we forget the happiness and blissful life of an innocent childhood

He prepared for mankind.

That was only the beginning and God saw the end from the beginning, He knew most would not find their way or reject Him. Oh well, they're loss, not mine.

'Cause I think God made the dinosaurs first,but then they got extinct,then came garden of eden

Jesus is the New Adam and the Virgin Mary is the New Eve. It is good to honor them both by reciting the rosary carefully daily.