Answer: 280 children
Explanation: Each grade has 70 kids. You have 4 total grades (3rd, 4th, 5th, and 6th grade). You have to add the number of kids you have in every grade. In this case, 70 children in 3rd grade, 70 children in 4th grade, 70 children in 5th grade, and 70 children in 6th grade. The problem would look like this:
70 + 70 + 70 + 70
Then your answer is 280 when you add them all together!