Most people believe that on the SAT, blanks "don't count." They probably think that blanks don't count because a blank sounds like nothing or a zero, so leaving a question blank must cost zero points.
These people are wrong, and you can prove it to yourself with the answer to a simple question. What kind of SAT score would you have if you left every question blank?
Sorry, but blanks do count. How much? Every time you leave a question blank, you lose 10 points from your 2400 starting score. The cost of each blank varies a bit, but as a rough average, figure 10 points per blank.
If you leave 10 questions blank on the SAT, you lose 100 points; 20 questions, 200 points. And every time you lose points for a blank, you can never get those points back. Never.