Question

HIGHWAYS Interstate 90 is the longest interstate highway in the United States, connecting the cities of Seattle, Washington, and Boston,
Massachusetts. The interstate is 4,987,000 meters in length. If 1 mile = 1.609 kilometers, how many miles long is Interstate 90?
Oa 3.099,441 mi
Ob. 3099 mi
Oc. 8,024,083 mi
O d. 8024 mi

Answer 1

Answer:  Choice B)  3099 mi

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Explanation:

4,987,000 meters = 4,987 kilometers

Divide by 1000 to go from meters to kilometers. This is because 1 km = 1000 m. Or in short, we just chop off those last three zeros at the end.

Also, because 1 mile = 1.609 km (approximate), this means we divide by 1.609 when converting from km to miles

So,

4,987 km = 4987/(1.609) = 3,099.4406 miles approximately

This rounds to 3099 miles

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You can optionally show your work like this:

$4,987,000 \text{ m} * \frac{1 \text{ km}}{1000 \text{ m}}*\frac{1 \text{ mi}}{1.609 \text{ km}}\\\\ = \frac{4,987,000*1*1}{1000*1.609} \text{ mi} \\\\\approx 3099.4406 \text{ mi}\\\\ \approx \textbf{3099 mi}$

Notice that the "km" and "m" units cancel out when going from the first step to the second step. All that's left is the "mile" unit.