lalania1 wrote:
A chemical supply company has 60 liters of a 40% HNO3 solution. How many liters of pure undiluted HNO3 must the chemists add so that the resultant solution is a 50% solution?
A) 12
B) 15
C) 20
D) 24
E) 30
Perfect opportunity for the
Alligation and
Bruce Lee (when we make numerators equal)!
\(? = x\)
\(\frac{{60}}{{60 + x}} = \frac{{100 - 50}}{{100 - 40}} = \frac{{5 \cdot \boxed{12}}}{{6 \cdot \boxed{12}}}\,\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,60 + x = 72\,\,\,\,\,\,\,\,\,\,\, \Rightarrow \,\,\,\,? = x = 12\)
This solution follows the notations and rationale taught in the GMATH method.
Regards,
Fabio.
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