20 machines can do a work in 10days. How many machines are needed to complete the work in 40days?	Choices.
A) 10 B) 6 C) 4 D) 7 E) 5
Required number of machines = 20*10/40= 
<gadget id="calculator">20*10/40</gadget>
<output>5</output>
5   Answer is 5
<result>E</result>
20 machines can do a work in 10days. How many machines are needed to complete the work in 40days?