Five test scores have a mean (average score) of 90, a median (middle score) of 91 and a mode (most frequent score) of 94. Find the sum of the two lowest test scores.
If five test scores have a mean of 90, then the total 5x90=450. We already have the middle score (91) and the two top scores (94 and 94). So the equation is 450-91-94-94=171