F3 Math Problems again

(a)
Marks less than 10.5 = Marks between 1 and 10, so a = 13.
Marks less than 20.5 = Marks between 1 and 20, that is a + 12 = b
so b = 13 + 12 = 25.
Marks less than 30.5 = Marks between 1 and 30 = a + 12 + c = 36,
so c = 36 - a - 12 = 36 - 13 - 12 = 11.
Marks less than 40.5 = Marks between 1 and 40 = a + 12 + c + 14 = d,
so d = 13 + 12 + 11 + 14 = 50.
(b)
Total frequency = 50, so median is the average of the value of 25th and 26th mark = (20 + 21)/2 = 20.5 (same if using class mark to calculate).
(c) Mean = Sum of (frequency x class mark)/total frequency
= (5.5 x 13 + 15.5 x 12 + 25.5 x 11 + 35.5 x 14)/50 = 20.7


2014-12-21 21:32:32 補充：
(2.54)10^(-2014) - (1.35)10^(-2012) = 10^(-2014)[2.54 - (1.35)10^2] = 10^(-2014)[2.54 - 135]
= 10^(-2014)(-132.46)
so the expression = (5)10^10/10^(-2014)(-132.46) = -0.037747x 10^2024 = - 3.7747 x 10^2022.