There are 20 boys and 11 girls in the second grade and twice that number in the third grade. How many students are in grades 2 and 3? Let's think first. Chain of thought:
There are 20 + 11 = 31 students in second grade. There are 31 x 2 = 62 students in third grade. In total, there are 31 + 62 = 93 students.
Therefore, the answer is 93.