Quote:
Machines K, M, and N, each working alone at its constant rate, produce 1 widget in x, y, and 2 minutes, respectively. If Machines K, M, and N work simultaneously at their respective constant rates, does it take them less than 1 hour to produce a total of 50 widgets?
(1) x < 1.5
(2) y < 1.2
Many a times we are unable to remove the algebraic lens and quickly deep dive into using equations and variables to power through and get an answer.
Alas, I also went about the hard way to solve this:
Given: To produce 1 widget alone, K takes x minutes, M takes y minutes, and N takes 2 minutes.
Alone, in 1 minute, K produces \(\frac{1 }{ x}\) widgets, M produces \(\frac{1 }{ y}\) widgets, and N produces \(\frac{1 }{ 2}\) widgets.
Together, in 1 minute they produce = \(\frac{1 }{ x} + \frac{1}{y} + \frac{1}{2}\) widgets = say Z widgets
So, 1 minute --- Z widgets
Then, 1 widget --- \(\frac{1 }{ Z}\) minutes
Together, to produce 1 widget they take \(\frac{1 }{ Z}\) minutes.
Together, to produce 50 widgets they take \(\frac{1 }{ Z}*50\) minutes.
What is asked of us: is \(\frac{1 }{ Z}*50\) minutes \(< 1 \) hour?
Let's simplify this.
\(\frac{1 }{ Z}*50\) minutes \(< 60\) minutes [/m]
\(\frac{1 }{ Z}*50 < 60\)
\(\frac{50}{60} < Z \)
\(\frac{50}{60} < (\frac{1 }{ x} + \frac{1}{y} + \frac{1}{2}) \)
\(\frac{5}{6} - \frac{1}{2} < (\frac{1 }{ x} + \frac{1}{y}) \)
Is, \(\frac{1}{3} < (\frac{1 }{ x} + \frac{1}{y}) \)?
Statement 1: \(x < 1.5\)
\(\frac{1}{1.5} < \frac{1}{x}\)
\(\frac{2}{3} < \frac{1}{x}\)
So, we can confidently say that \(\frac{1}{3} < (\frac{1 }{ x} + \frac{1}{y}) \) because \(\frac{1}{y} \) cannot be negative.
1 is sufficient.
Statement 2: \(y < 1.2\)
\(\frac{1}{1.2} < \frac{1}{y}\)
\(\frac{5}{6} < \frac{1}{y}\)
So, we can confidently say that \(\frac{1}{3} < (\frac{1 }{ x} + \frac{1}{y}) \) because \(\frac{1}{x} \) cannot be negative.
2 is sufficient.
Answer: D.