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Mary drove to Birmingham Airport at 55 miles per hour for the first two hours and then at 70 miles per hour for the remainder of the jorney. Her average speed for the entire journey was 60 miles per hour. How long did Mary's journey to Birmingham Airport take?
If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.
This problem is taken from the UKMT Mathematical Challenges.
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