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put this solution on YOUR website!
We find the LCM of 18 and 21
Line up the prime factorizations,
then bring them down to the bottom line
and multiply:
18 = 2×3×3
21 = 3×7
-------------
LCM = 2×3×3×7 = 126
Answer = 126 minutes [which is 6 complete laps for
the slower runner, since 6×21=126
and 7 complete laps for the faster
runner, since 7×18 also = 126.
Edwin