If 25 typists can type 60 letters in 20 minutes, then how many letters will 75 typists working at the same rate complete in 1 hour?  Choose the correct choice from the following options
A) 270	B) 540	C) 610	D) 510	E) 500
No. of letters typing by 25 typists in 20 minutes = 60   No. of letters typing by 25 typists in 60 minutes = 60*3= 
<gadget id="calculator">60*3</gadget>
<output>180</output>
180   No. of letters typing by 75 typists in 60 minutes= 180/25*75= 
<gadget id="calculator">180/25*75</gadget>
<output>540</output>
540   Answer : 540
<result>B</result>
If 25 typists can type 60 letters in 20 minutes, then how many letters will 75 typists working at the same rate complete in 1 hour?