In a trend that scientists attribute at least in part to global warming a certain floating cap of sea ice has been shrinking since 1980 The ice cap always shrinks in the summer and grows in winter Average minimum size of the ice cap in square miles can be approximated by A r In 2013 the radius of the ice cap was approximately 793 and was shrinking at a rate of approximately 4 1 mi yr How fast was the area changing at that time The area was changing at a rate of Round to the nearest integer as needed in 2013 mi yr mi yr yr mi mi yr mi yr