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Printimc
algebra intermediate
Problem
Danica drove her new car on a trip for a whole number of hours, averaging miles per hour. At the beginning of the trip, miles was displayed on the odometer, where is a -digit number with and . At the end of the trip, the odometer showed miles. What is ?
(A)
(B)
(C)
(D)
Solution
Let be the number of hours Danica drove. Note that can be expressed as . From the given information, we have . This can be simplified into by subtraction, which can further be simplified into by dividing both sides by . Thus we must have . However, if , then , which is impossible since must be a digit. The only value of divisible by and less than or equal to is . From this information, . Combining this with the inequalities and , we have , which implies , so , and . Thus
Final answer
D