離差的量度(1題,急!!!)

咁岩我學校都係教緊呢課書@@
入正題
i)設x該班的學生人數,因為超過50的學生共有27名, 50分是Q2的位置,Q2以上是有總數的75%
x(75%)=27
x=36人

ii) 由i)得知該班總數是36人, 低於70的學生=Q3以下的學生,有75%
所以36(75%)=27人

希望幫到你,有唔明可以再明.

i)
Marks over 50 means those students are above the 1st quartile, that means 3/4 of the total students are over 50 marks = 27, therefore total no. of students in class = 27 x 4/3 = 36.
ii)
Marks under 70 means students are below the 3rd quartile, that is 3/4 students are under 70 marks = 36 x 3/4 = 27 students.