16. After 9 weeks Mikayla has an average mark of 5 out of 10 in the weekly spelling tests. What is the minimum number of extra weeks now required to raise her average to 7 ?
(A) 4
(B) 5
(C) 6
(D) 7
(E) 8

Answer

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Answer

\boxed{6}

Steps

Step 1 ：Find the total marks Mikayla has currently: Total marks = average * number of weeks = 5 * 9

Step 2 ：Let x be the number of extra weeks required. Solve for x in the equation: \(\frac{5 * 9 + 10 * x}{9 + x} = 7\)

Step 3 ：\boxed{6}