A factory normally produces x units per working day. In a month with 22 working days, no units are produced in the first y working days because of a strike. How many units must be produced per day on each of the rest of the working days of the month in order to have an average of x units per working day for the entire month?
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Got D pretty quickly once I set total = 22x. The strike days produce nothing, so the remaining days have to make up the whole thing.
Nice, I overcomplicated it at first but that's the clean way.
Wait, why do we count the strike days in the average at all? Wouldn't the average just be over the days they actually worked?
That tripped me up too. The word 'entire' is doing a lot of work here.
This one felt easier than most work-rate problems. Plugging in x = 10 and y = 2 made the answer obvious.
Can someone explain why (E) is wrong? I keep getting lost in the algebra on this one.
Check the units: total units should be 22x, so anything that doesn't simplify to that is off.
What it tests
Your ability to combine individual work rates, usually by working with the fraction of a job completed per unit of time.
Common trap
Adding the times instead of the rates, or forgetting to take the reciprocal when combining rates.