Bunuel wrote:
A metal company's old machine makes bolts at a constant rate of 100 bolts per hour.The company's new machine makes bolts at a constant rate of 150 bolts per hour. If both machines start at the same time and continue making bolts simultaneously, how many minutes will it take the two machines to make a total of 300 bolts?
A. 36
B. 72
C. 120
D. 144
E. 180
\(?\,\,\, = \,\,\,T\,\,\left[ {\min } \right]\)
Perfect opportunity for
UNITS CONTROL, one of the most powerful tools carefully explained in our course!
\(300\,\,{\text{bolts}}\,\,\,\,{\text{ = }}\,\,\,\,\left( {\frac{{100\,\,{\text{bolts}}}}{{60\,\,\min }}} \right)\,\, \cdot \,\,T\,\,\min \,\,\, + \,\,\,\left( {\frac{{150\,\,{\text{bolts}}}}{{60\,\,\min }}} \right)\,\, \cdot \,\,T\,\,\min\)
\(300\,\,\, = \,\,\,\frac{{5 \cdot \boxed2}}{{3 \cdot \boxed2}}T\,\, + \,\,\frac{{5 \cdot \boxed3}}{{2 \cdot \boxed3}}T\,\,\, = \,\,\,\frac{{25}}{6}T\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,T = \frac{6}{{25}}300 = 6 \cdot 3 \cdot 4 = 72\)
The correct answer is therefore (B).
We follow the notations and rationale taught in the
GMATH method.
Regards,
Fabio.
_________________
Fabio Skilnik ::
GMATH method creator (Math for the GMAT)
Our high-level "quant" preparation starts here:
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