Skip over navigation
This was a tricky problem but Zach sent in a very comprehensive answer. He has used a table to show the probabilities and has looked at what would happen if the rate of infection was higher. You can see his full solution here.
The ELISA Test
Age 14 to 18
Challenge Level 
This was a tricky problem but Zach sent in a very comprehensive answer. He has used a table to show the probabilities and has looked at what would happen if the rate of infection was higher. You can see his full solution here.
Related Collections
You may also like
Cyclic Quad Jigsaw
A picture is made by joining five small quadrilaterals together to make a large quadrilateral. Is it possible to draw a similar picture if all the small quadrilaterals are cyclic?
Angle Trisection
It is impossible to trisect an angle using only ruler and compasses but it can be done using a carpenter's square.
Beelines
Is there a relationship between the coordinates of the endpoints of a line and the number of grid squares it crosses?