In previous scaffolded problems, where the student's answers were approximations, we used the method of giving credit for approximations that were close enough, but then told him/her to use the exact values which we gave - of course this assumed the answer to the first part was "close enough", so the next section would open.

when the answer is not correct, I don't know how to open the next section.

I'll be reading on the hidden answers and get back on that later

thanks