Beatrice traveled the last 220 miles of the trip at 55 miles per hour. The entire trip covered 430 miles and took 7 hours. What was her rate for the first 210 mile?
Beatrice traveled the last 220 miles of the trip at 55 miles per hour. The entire trip covered 430 miles and took 7 hours. What was her rate for the first 210 mile?
Let Beatrice's average speed for the first 210 miles = S
220/55 + 210/S
Solve for S:
4 + 210/S = 7
Bring 4 + 210/S together using the common denominator S:
(2 (2 S + 105))/S = 7
Multiply both sides by S:
2 (2 S + 105) = 7 S
Expand out terms of the left hand side:
4 S + 210 = 7 S
Subtract 7 S + 210 from both sides:
-3 S = -210
Divide both sides by -3:
Answer: |S = 70 - miles per hour, her speed for the first 210 miles.
