Putting down the answers for (a) and (b) for those interested.

Let me know if my answers are wrong.

## SPM Add Math Probability Q33

33 .

The results of a Mathematics test of the students in Form 5 Red are tabulated according to the ratio of the number of students who achieve each grade, as shown above. If the test marks are normally distributed with mean 80 and standard deviation 5, find

(a) the minimum mark requirets to obtain grade A,

(b) the passing mark if grade \mathrm{C} is considered fail,

(c) the mean mark for the class if a student who obtained 80 marks is not taken into account when calculating the new mean.

### SPM Add Math Probability Q33 Solution

Hi Xiao Min. welcome to SKORA!

**The answer is just 80** I believe? As students with the mean mark added/removed from the data group will not affect the new mean.

Let’s say a data group (marks) of 70, 80, 90 will give a mean of 80.

When a student with mark of 80 is added, the mean will still be 80.

Similarly when the student with mark of 80 is removed, the mean is still 80.

If the answer is not 80, let me know.

Thanks for your respon! Your answer is exactly right!