Maths. F.3

首先要判斷x係o係邊個位
52,60,70,83,100
如果係細過60, 咁個median就會係(60+70)/2=65
如果係大過83, 咁個median就會係(70+83)/2=76.5
而家個median係72.5, 即係x應該o係70既左或右一個位
median=(70+x)/2=72.5
x=75

做數先要理解問題, 再適當既方法或者式

先重組data,有小至大52,60,70,83,100, 我們要估計x的位置,
可能性
1.如果x放在52和60中間或52之前,median 是(60+70)/2,不等如72.5
2.如果x放在83和100中間或100之後,median 是(70+83)/2,不等如72.5
所要只有第3個可能性,就是在60和70中間或70和83中間,兩個可能性的計法都是(x+70)/2=72.5, x+70=145, x=75,x在70和83中間

List the number like that :52,60,70,83,100,x

the median is the mean of the middle two data

the median is larger than 70

so x is the forth number(第4個數)

(x+70)/2=72.5

x+70=145

x=75

x = 75

the scores have to be :

52, 60, 70, 75, 83, 100 for the median to be equal to 72.5.

X has to be the middle of 70 and a number between 83 & 70. therefore:

(70 + x)/2 = 72.5
x=75

∵median=72.5
∴(83+100+52+70+60+x)/6=72.5
365+x=72.5*6
365+x=435
X=70

(83+100+52+70+60+x)/6 = 72.5
(365+x)/6 = 72.5
365+x = 435
x = 70

83+100+52+70+60+x
-------------------------------- = 72.5
6


x=72.5x6-100-83-52-70-60
=70