Perhaps you interpreted the question slightly differently, I took it as the ball was being thrown upwards but we were only measuring the position (with some device) every 0.1 s. Therefore, you can still assume the ball to reach a max height at some fraction not at 0.1 s, we just don't have a precise enough measurement to catch this so we're forced to round to 0.1 s because that's the precision of the device.
This is a common limitation for modeling, so I'm confused as to why this isn't a reasonable approach in your view.

this was the first thing i tried but it wouldn't work for me how was it accepted for you guys?