The multiple-choice questions will take her a total of 30 * 15 = <<30*15=450>>450 minutes.
The fill-in-the-blank questions will take her a total of 25 * 30 = <<25*30=750>>750 minutes.
The test will take her a total of 450 + 750 = <<450+750=1200>>1200 minutes to study for.
Therefore, Martiza will need to study a total of 1200 / 60 minutes = <<1200/60=20>>20 hours.
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