Carlos biked 139 eighths miles on Saturday and 135 sevenths miles on Sunday. On which day did he ride further and by how much?

Write both distances with denominator 56: Saturday was 139/8 = 973/56 miles, and Sunday was 135/7 = 1,080/56 miles. Sunday’s distance is greater by 1,080/56 − 973/56 = 107/56 = 1 51/56 miles. Therefore, Carlos rode further on Sunday by 1 51/56 miles.

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