MathNet 2024-part-05 — 168 problems (EN–VI) Question 164

A data set containing 20 numbers, some of which are $6$, has mean $45$. When all the $6$s are removed, the data set has mean $66$. How many $6$s were in the original data set?
(A) 4 (B) 5 (C) 6 (D) 7 (E) 8