a is twice as fast as b. if b alone can do a piece of work in 18 days, in what time can a and b together complete the work?  Choose one.
A) 10 B) 16 C) 18 D) 6 E) 12
<gadget id="calculator">1 / 18</gadget>
<output>1/18 = around 0.055556</output>

<gadget id="calculator">(1/18) * 2</gadget>
<output>1/9 = around 0.111111</output>

<gadget id="calculator">(1/18) + (1/9)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">1 / (1/6)</gadget>
<output>6</output>

<result>D</result>
a is twice as fast as b. if b alone can do a piece of work in 18 days, in what time can a and b together complete the work?
inverse(add(divide(const_1, 18), multiply(divide(const_1, 18), const_2)))
"a can do the work in 18 / 2 i . e . , 9 days . a and b ' s one day ' s work = 1 / 9 + 1 / 18 = ( 2 + 1 ) / 18 = 1 / 6 so a and b together can do the work in 6 days . answer : d"