To solve, get the total (11 boys + 9 girls = 20 total students). Put the number of boys over the total, representing it as a fraction, 11/20. Now convert this t a precent by dividing 11 by 20 and multiplying the result by 100.
11 divided by 20 = 0.55
0.55 times 100 = 55%
So, 55% is your final answer. I hope this helps and have a great day!