If 20 typists can type 60 letters in 20 minutes, then how many letters will 30 typists working at the same rate complete in 1 hour?
Choose one:	A) 240	B) 200	C) 270	D) 300	E) 310
No. of letters typing by 20 typists in 20 minutes = 60   No. of letters typing by 20 typists in 60 minutes = 60*3= 
<gadget id="calculator">60*3</gadget>
<output>180</output>
180   No. of letters typing by 30 typists in 60 minutes= 180/20*30= 
<gadget id="calculator">180/20*30</gadget>
<output>270</output>
270   Answer : 270
<result>C</result>
If 20 typists can type 60 letters in 20 minutes, then how many letters will 30 typists working at the same rate complete in 1 hour?