p can do a work in the same time in which q and r together can do it. if p and q work together, the work can be completed in 10 days. r alone needs 20 days to complete the same work. then q alone can do it in  Options.
A) 20 B) 22 C) 25 D) 27 E) 40
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/10) + (1/20)</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">(3/20) / 2</gadget>
<output>3/40 = around 0.075</output>

<gadget id="calculator">(3/40) - (1/20)</gadget>
<output>1/40 = around 0.025</output>

<gadget id="calculator">1 / (1/40)</gadget>
<output>40</output>

<result>E</result>
p can do a work in the same time in which q and r together can do it. if p and q work together, the work can be completed in 10 days. r alone needs 20 days to complete the same work. then q alone can do it in
divide(const_1, subtract(divide(add(divide(const_1, 10), divide(const_1, 20)), const_2), divide(const_1, 20)))
"work done by p and q in 1 day = 1 / 10 work done by r in 1 day = 1 / 20 work done by p , q and r in 1 day = 1 / 10 + 1 / 20 = 3 / 20 but work done by p in 1 day = work done by q and r in 1 day . hence the above equation can be written as work done by p in 1 day ã — 2 = 3 / 20 = > work done by p in 1 day = 3 / 40 = > work done by q and r in 1 day = 3 / 40 hence work done by q in 1 day = 3 / 40 â € “ 1 / 20 = 1 / 40 so q alone can do the work in 40 days answer is e ."