Two women start walking toward each other from two ends of a bridge at the same time. They both leave at dawn. When they meet, it is 12pm. When the first woman reaches the other end of the bridge, it is 4pm. When the second woman reaches the end of the bridge, it is 9pm. Both women walk at different, but constant, rates. What time is dawn?
We could plug in the answer choices and our own value for the length of the bridge.awilhelm wrote:Two women start walking toward each other from two ends of a bridge at the same time. They both leave at dawn. When they meet, it is 12pm. When the first woman reaches the other end of the bridge, it is 4pm. When the second woman reaches the end of the bridge, it is 9pm. Both women walk at different, but constant, rates. What time is dawn?
Answer choice: dawn = 6am.
Time for first woman = 4pm - 6am = 10 hours.
Time for second woman = 9pm - 6am = 15 hours.
Plug in bridge = 30 meters.
Rate for first woman = d/t = 30/10 = 3 meters per hour.
Rate for second woman = d/t = 30/15 = 2 meters per hour.
Combined rate for the two women as they walk toward each other = 3+2 = 5 meters per hour.
Time for them to meet = d/(combined rate) = 30/5 = 6 hours.
6am + 6 hours = 12pm. Success!
