Hello Wendy,

It is due to the way computers work. For example, 10 ¢ is equal to $ 0.10 but computers use binary numbers and the binary representation of 0.1 is 0.000110011001100... which only gives an approximation of decimal 0.1.

Even if you expect the answer to be $ 0.10, the computer will check against a value of $ 0.0999755859375. In other words, the computer cannot check an "exact" value of $ 0.10.

It might seem a bit silly at first, but this is how computers work. All you have to do is set the "Grading criterion", in the question settings, to "Relative error < 0.001". Then everything should work fine.