What does 5以内 mean in 数学作业要在3分钟之内完成90道5以内的加减法题? 数学作业要在3分钟之内完成90道5以内的加减法题


I can understand it as:


  The Math homework (you) must complete 90 questions of addition and subtraction within 3 minutes under 5. (what the heck?)


What does 5以内 mean in this sentence?
It means questions that only involves positive numbers no larger than 5. For example, asking questions like "2+2=?" or "4-3=?".