it will take 16 days for mary to complete a certain task alone. she worked for 8 days before she was joined by her sister. both of them completed the remaining task in 2 and half days. if her sister had joined her when she started the task, how many days would it have taken?  Choose the correct option.
A) 6	B) 8	C) 2	D) 5	E) 4
<gadget id="calculator">1 / 8</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">1 / 16</gadget>
<output>1/16 = around 0.0625</output>

<gadget id="calculator">(1/8) / (1/16)</gadget>
<output>2</output>

<gadget id="calculator">2 + 3</gadget>
<output>5</output>

<result>D</result>
it will take 16 days for mary to complete a certain task alone. she worked for 8 days before she was joined by her sister. both of them completed the remaining task in 2 and half days. if her sister had joined her when she started the task, how many days would it have taken?
add(divide(divide(const_1, 8), divide(const_1, 16)), const_3)
explanation : mary and her sister complete half work in 2.5 days = > they can complete whole work in 5 days answer : option d