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Mandy, Callie, and Kate were running a race of 1500 meters. Mandy won.
At the moment when Mandy crossed the finish line, she was 300 meters ahead of Callie and 420 meters ahead of Kate.
If Callie and kate kept running at the same rates as they have run so far, how many meters ahead of Kate will Callie be when she crosses the finish line?
We can say, that while C ran 1500-300 = 1200 meters, K ran 1500-420 = 1080 meters
K's speed =
= .9C speed
While C runs the final 300 meters, K runs .9*300 = 270 meters
therefore at the 1200 meter point, K was 120 m behind C, and lost another 30 meters when C ran the last 300 m
120 + 30 = 150 meters behind when C crossed the finish line