Question 1158568
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Consider the least common multiple of the two given times, which is 20 minutes.<br>
In 20 minutes, Ed can drop 20/4=5 pieces of luggage and Hew can drop 20/5=4 pieces of luggage.  So in 20 minutes together, the two of them can drop 5+4=9 pieces of luggage.<br>
18 pieces is twice that number; so it will take them twice as long -- 40 minutes -- to drop 18 pieces of luggage.<br>