ERIN RIDES HER BIKE AT A CONSTANT SPEED FOR 21 MILES SHE THE

ERIN RIDES HER BIKE AT A CONSTANT SPEED FOR 21 MILES. SHE THEN RETURNS HOME AT THE SAME SPEED BUT TAKES A DIFFERENT ROUTE. HER RETURN TRIP TAKES ONE HOUR LONGER AND IS 26 MILES. FIND HER SPEED.

Solution

1st Leg:
distance = 21 miles ; rate = x mph ; time = 21/x
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2nd Leg:
distance = 26 miles ; rate = x mph ; time = 26/x
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Equation:
2nd time - 1st time = 1 hr
26/x - 21/x = 1
26 - 21 = x
x = 5 mph