Answer:
The Answer is 30 Problems.
Explanation:
Here is an explanation.
Knowing that this is the equation, simply insert a random number and multiple it by .90. We know it can't be 27 or lower because that is 90% of problems on the test. So you may start at 28 and overtime slowly increase. Based on how the big the number is, you make your judgement on how small or big you start with.
30 x .90 = 27