9514 1404 393
Answer:
34
Step-by-step explanation:
In order to divide some multiple of 15 chocolate bars evenly by 21, the number of bars must be a multiple of the LCM of 15 and 21, which is 105. That number is 7 times 15, indicating the number of boys in the class must be a multiple of 7. The only number between 30-20 = 10 and 40-20 = 20 that is a multiple of 7 is 14.
There must be 14 boys in the class, so 34 students in total.
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The boys brought a total of 210 chocolate bars, so each girl and the teacher received 10 of them.
