Gretchen walked more than a whole mile on both days combined, because if on Saturday she walked 7/10 miles, she would have only needed 3/10 of a mile more to walk on Sunday to make 1 mile. On Sunday, however, she walked 3/4 miles, and using common knowledge, we know that 3/4 miles is more than 3/10. Thus, Gretchen walked more than a mile on both days combined.
