Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:
1) Angle of a triangle inscribed in a semicircle is 90. Here, the angle is 90, so it is a semi circle (corollary) => AC is a diameter
2) AB/BC = 3/4. Perhaps they are baiting that we might assume AB:BC:AC = 3:4:5 and therefore conclude angle ABC is 90*. But that is not the case. It does not say BC:AC is 4:5.
Can't get more information from this statement