SOLUTION: On Saturday morning, Lynn walked for 2 hours and then ran for 30 minutes. If she ran twice as fast as she walked and she covered 12 miles altogether, then how fast did she walk?

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Question 9701: On Saturday morning, Lynn walked for 2 hours and then ran for 30 minutes. If she ran twice as fast as she walked and she covered 12 miles altogether, then how fast did she walk?
Answer by prince_abubu(198) (Show Source):
You can put this solution on YOUR website!
If she ran and walked, she must have a running speed and a walking speed. Let's call these R and W, running and walking respectively.

They tell us that her running speed is double her walking speed. That translates to . The running speed is already faster. It makes sense to "inflate" the slower walking speed by multiplying it by 2 to match the running speed.

We are going to use that formula rate x time = distance, keeping in mind that we have to add up her walking distance and running distance to cover the total 12 miles. Her walking distance would be because she would be walking at W mph for two hours. Her running distance would be . Remember that we have the relationship so we simply replaced the R with a 2W in the running distance expression. The 0.5 would be equivalent to the 30 minutes. Since we're working with hours and miles per hour, we need to convert the minutes to hours.

<------- Start

<---- simplify

<---- combine like terms

<---- Her walking speed is 4 mph. If her running speed was double that, the running speed would be 8 mph.