A machine, working at a constant rate, manufactures 18 pens in 30 minutes. How many pens does it make in 1 hr 45 min?
Select the correct option.
A) 63
B) 65
C) 62
D) 60
E) 45

Rationale: change 1 hr 45 min to 105 min . for this , we need to set up a simple proportion of pens per time 18 / 30 = s / 105 the absolutely worst thing you could do at this point in the problem is to cross - multiply . that would be a supremely unstrategic move . instead , cancel before you multiply . for what we can see this post . we can cancel 18 / 30 as 6 / 10 6 / 10 = s / 105 we can cross - multiply . 10 * s = 6 * 105 = 630 if we divide both sides by 10 , s = 63 the machine would be 63 pens in 1 hr 45 min . answer : a
Answer: A