Question 1157207
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Here is alternative to the standard algebraic solution method shown by the other tutor.<br>
Consider the least common multiple of the two given times: the LCM of 24 and 30 is 120.<br>
In 120 hours, the crew of 2 could put siding on 120/30 = 4 houses; the crew of 3 could put siding on 120/24 = 5 houses.  So in 120 hours the two crews together could put siding on 4+5=9 houses.<br>
So the number of hours it would take the two crews together to put siding on 1 house is 120/9 = 40/3, or 13 1/3 hours, or 13 hours 20 minutes.<br>