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Answer:
1.53 minutes faster
Step-by-step explanation:
A question of this nature can be answered a number of ways. Often, when athletes compare speeds over a course of a specific length, they do it by comparing times.
Here, Jill"s time is ...
21.00 -19.47 = 1.53
minutes less than Grace"s time.
Jill swam a mile 1.53 minutes faster than Grace did.
