A farming field can be ploughed by 6 tractors in 4 days. When 6 tractors work together, each of them ploughs 120 hectares a day. If two of the tractors were moved to another field, then the remaining 4 tractors could plough the same field in 5 days. How many hectares a day would one tractor plough then?
Correct answer: D
Explanation
If each of 66 tractors ploughed 120120 hectares a day and they finished the work in 44 days, then the whole field is: 120⋅6⋅4=720⋅4=2880120⋅6⋅4=720⋅4=2880 hectares. Let's suppose that each of the four tractors ploughed xx hectares a day. Therefore in 5 days they ploughed
5⋅4⋅x=20⋅x5⋅4⋅x=20⋅x hectares, which equals the area of the whole field, 2880 hectares.
So, we get 20x=288020x=2880
x=288020=144x=288020=144. Hence, each of the four tractors would plough 144 hectares a day.
D
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AQuA-RAT items are crowdsourced algebra problems, not ACT questions. They carry five answer choices in the pre-2025 ACT Mathematics style and no ACT reporting category. Useful for drilling Preparing for Higher Math content; not a substitute for a real form.