Hello Sujatha,

Yes you can score 80 percentile very easily in 20 days but it is of no use. For best colleges through JEE-Main exam you need to score at least 98 percentile in JEE-Main. Here are some tips through which you can ace the examination in last 20 days :-

• Solve previous year papers as many as you can according to the mentioned time, it improves your time management skill.
• All formulas should be in your tongue.
• Focus on numerical section rather than theory section.
• Don't go for theory reading in last days, you can read your notes thoroughly.
• Stay healthy, avoid junk food and oily food.
• Adhere to the Exam Day Guidelines to avoid mistakes.

For more preparation tips of JEE-Main you can read this article .

I hope this answer helps you.

All The Best!!