If 20 students can complete 20 project using 20 machines in 20 mandays, in how many mandays can 12 students complete 12 project using 12 machines?
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Wait, is it really that straightforward? I got 20, but the 705-805 tag made me second-guess.
Same here, I was expecting some twist with the machines.
Yeah, the high difficulty is misleading. It's just a proportion.
I'm confused: why do the machines not change the mandays? If 20 machines do 20 projects, doesn't each machine do 1 project? Then 12 machines do 12 projects, so it's the same ratio?
That's what I thought too, but then why is it rated so hard?
Because people overcomplicate it. The machines are just a distractor.
Took me a while but I finally saw it: 20 students, 20 projects, 20 machines, 20 mandays. So 1 student, 1 project, 1 machine takes 20 mandays? No, that's not right either. Let me redo.
Actually, if you halve students and projects and machines, the mandays stay the same because the ratio is unchanged.
Exactly, it's a classic GMAT trick. They want you to think it's proportional to each variable separately.
This is a 705-805? I got 20 days in like 30 seconds. Maybe I'm missing something? But the logic seems solid: all quantities scale down proportionally, so time remains 20.
Don't worry, it's probably just a hard question because of the trap. You're good.
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.