Jennifer's home is 5 miles away from the first museum, so the round trip back and forth is 5 miles there + 5 miles back = <<5+5=10>>10 miles altogether.
On another day Jennifer goes to a museum 15 miles away + 15 miles to return home = <<15+15=30>>30 miles total.
Combined, Jennifer travels 10 miles on the first day + 30 miles on the second day = <<10+30=40>>40 miles Jennifer travels total.
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