Show how you can add and subtract mentally. Try to do thes problems without pencil and paper.

National Monuments Name		State		Acres
George Washington Carver		Missouri		$210$
Navajo		Arizona		$360$
Fort Sumter		South Carolina		$200$
Russell Cave		Alabama		$310$

1) How many more acres are there at Navajo Monument than at George Washington Carver Monument? more acres.

2) How many acres are there at Fort Sumter and Russell Cave combined? acres.