alleryStart learning →Machine A produces a batch in 3 hours; machine B produces the same batch in 2 hours. How long do they take together?
A5 hours
B2.5 hours
C1.5 hours
D1.2 hours
Answer & Solution
Correct answer: D. 1.2 hours
Rates add when machines work in parallel: $1/3 + 1/2 = 1/x$.
**Common denominator 6:** $2/6 + 3/6 = 5/6$, so $1/x = 5/6$ and $x = 6/5 = 1.2$ hours, that is 1 hour 12 minutes.
**Option A wrongly adds the individual times; option B halves that sum.**
Related questions
The graph of $f(x) = |x| + 2$ is the graph of $y = |x|$ shifted in which direction?Find the vertex of the parabola $y = x^2 - 2x - 3$.A line has slope 2. What is the slope of any line perpendicular to it?Find the distance between the points $Q(-2, -3)$ and $R(4, 1.5)$ in the xy-plane.If 10000 rupees is invested at a simple annual interest rate of 6 percent, what is the valA 12g mixture is 40% vinegar by weight. How many grams of oil must be added so the new mixEllen has three exam scores 82, 74, and 90. What score on her next exam will give her an aWhat is the domain of the function $g(x) = x^3 + qrt{x + 2} - 10$?