To figure this one out, Peter, you need to create an equation that embodies the question:
If 33=70%, what is 100%?
*** I am not going to give you the answer, so I am going to change 33 to 63. ***
Now, what is 70%? 70 per cent (per cent means roughly "for a hundred" in Latin, or out of 100) is 70/100, or simplified, 7/10
So, 63 = 70% of how many total questions? "Of" in mathematics means to multiply, so,
63 = 70% times y.
So,
63 = .7y
Then, divide each side by .7 to get the equation in shape to solve for y
y = 63 /.7
y = 90
You can check by then dividing 63 by y (the number of questions). This way, you can see what percent of the total questions the student got right).
63/90 = .7 = 7/10 = 70%
So, 100% would equal 90 questions.