SOLUTION: 3. We had to go 30km through the city and then 30km through the country. Through the city we average 40km/h and through the country we averaged 60km/h. Our average speed for the en

Algebra ->  Average -> SOLUTION: 3. We had to go 30km through the city and then 30km through the country. Through the city we average 40km/h and through the country we averaged 60km/h. Our average speed for the en      Log On


   

Question 885443: 3. We had to go 30km through the city and then 30km through the country. Through the city we average 40km/h and through the country we averaged 60km/h. Our average speed for the entire journey was
a. 44 b. 48 c. 50 d. 45
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Average speed is always ( total distance ) / ( total time )
+30+=+40t%5B1%5D+
+t%5B1%5D+=+3%2F4+
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+30+=+60t%5B2%5D+
+t%5B2%5D+=+1%2F2+
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Average speed = +%28+30+%2B+30+%29+%2F+%28+3%2F4+%2B+1%2F2+%29+
Average speed = +60+%2F+%28+5%2F4+%29+
Average speed = +%284%2F5%29%2A60+
Average speed = 48 km/hr
The answer is b.