## anonymous 5 years ago Nadia has an average score of 70 after 5 tests. What is the minimum number of tests that Nadia has to score a 100 on to get the average score to at least 89?

Let $$n$$ be the number needed. So we want to have $$5\cdot70+100n\geq 89(n+5)$$ $$350+100n \geq 89n+445$$ $$11n\geq 95$$ $$n\geq 95/11$$ So at least $$n=9$$.