Suppose you make six round trips to visit a sick aunt and wish to record your mileage to the nearest mile. You forget the original odometer reading, but you do remember that the units digit has increased by 8 miles. If you know that your aunt lives somewhere between 26 and 31 miles from your house, how far exactly is her house?

Question

Suppose you make six round trips to visit a sick aunt and wish to record your mileage to the nearest mile. You forget the original odometer reading, but you do remember that the units digit has increased by 8 miles. If you know that your aunt lives somewhere between 26 and 31 miles from your house, how far exactly is her house? ​

Quizplus · Accepted Answer

Since the units digit increased by 8 after six round trips, the total distance for one round trip must end in a 3 or an 8 (because 6 trips would increase the units digit by 18, rolling over once). Among the given options, only 29 miles ends in a 9, which would result in the units digit increasing by 8 after six round trips (since 29 miles x 6 = 174 miles, and the units digit of the total distance would increase from 1 to 9).

Suppose You Make Six Round Trips to Visit a Sick