If 10 typists can type 30 letters in 30 minutes, then how many letters will 40 typists working at the same rate complete in 1 hour?  Choose the correct choice from the following answers
A) 200  B) 210  C) 205  D) 225  E) 240
No. of letters typing by 10 typists in 30 minutes = 30   No. of letters typing by 10 typists in 60 minutes = 30*2= 
<gadget id="calculator">30*2</gadget>
<output>60</output>
60   No. of letters typing by 40 typists in 60 minutes= 60/10*40= 
<gadget id="calculator">60/10*40</gadget>
<output>240</output>
240   Answer : 240
<result>E</result>
If 10 typists can type 30 letters in 30 minutes, then how many letters will 40 typists working at the same rate complete in 1 hour?