Question

No of students	Marks
10	80
5	75
5	70
2	60
2	55
1	20

Tina's score was accidentally omitted from the list. When her score is added, the average (arithmetic mean) score for the class does not change. What is Tina's score?

• A. 68
• B. 69
• C. 70
• D. 71

Answer 1

The correct option is D 71

If the Average score of the class does not change when Tina's score is added .

So Tina's score is equal to the average score.

$\therefore$ Average $=$ $\frac{10\times 80+5\times 75+70\times 5+60\times 2+55\times 2+\times 20\times 1}{10+5+5+2+2+1}$

$\Rightarrow \frac{800+375+350+120+110+20}{25}=\frac{1775}{25}=71$

$\therefore$ Tina's score $=71$