If 10 typists can type 20 letters in 20 minutes, then how many letters will 40 typists working at the same rate complete in 1 hour?	Select the correct option:
A) 220
B) 210
C) 200
D) 240
E) 260
No. of letters typing by 10 typists in 20 minutes = 20   No. of letters typing by 10 typists in 60 minutes = 20*3= 
<gadget id="calculator">20*3</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>D</result>
If 10 typists can type 20 letters in 20 minutes, then how many letters will 40 typists working at the same rate complete in 1 hour?