中一數學問題

1)Let y be the no. of students
y(55%) - y(30%) = 60
y(55%-30%) = 60
y(25%) = 60
y = 60/(25%)
y = 240
所以中一級的學生人數是240

2a)The no.of students who took bus to school yesterday:
= 1500(80%) - 1500(80%)(20%)
= 1200 - 1200(20%)
= 1200 - 240
= 960

b)The no. of students who didn't take bus to school yesterday:
= 1500 - 960
= 540

(1) 設中一級學生人數為 y 人，
自備午飯人數 = 30%y；購買飯盒人數 = 55%y
因此 55%y - 30%y = 60
0.25y = 60
y = 240 人

(a) 1500*80% = 乘巴士上學人數
乘巴士上學人數*20% = 昨天改乘地鐵人數
因此 1500*80%*20% = 240 人昨天乘地鐵

(b) 1500*(1-80%) = 不乘搭巴士上學人數 = 300 人
不乘搭巴士上學人數 + 昨天乘地鐵人數
= 300 + 240 = 540 人 = 昨天不乘搭巴士上學的學生人數

(1)55%-30%=25%=人數之差=60人
中一級的學生人數=60/25%=240人

(2a)1500x(80%-20%)=900人
(2b)1500-900=600人

2006-12-09 13:24:34 補充：
(2a)1500x80%x(1-20%)=960人(2b)1500-960=540人

1. let x be the total number of students.

(50%-30%)x = 60
20%x = 60
x = 60/ 20%
x = 300
- The total number of F.1 pupils is 300.

2.a) 1500 X (80%-20%)
= 1500 X 60%
= 900.

b) 1500 X 20%
= 300.


Hope it can help you =]`

2006-12-09 13:21:08 補充：
edited for no.1 //1. let x be the total number of students.(55%-30%)x = 6025%x = 60x = 60/ 25%x = 240- The total number of F.1 pupils is 240