Answer:
200 students must agree to attend in order for the school to have the festival.
Explanation:
200 is 40% of 500. We can also use fractions to figure this out.
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For 100 to become 500 it must be multiplied by 5. And whatever we do to the denominator we have to do to the numerator. So we multiply 40 × 5 = x
x = 200
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