有2條英文數學題唔識 help~

蔚欣

2009-04-19 12:01 am

mean= 平均數
1.
It is known that the mean of the numbers of push-ups done by S3a
boys in a minuteis 21 ,by the S3A girls is 9, and by the whole class is
13.4. If there are 30 students in S3A, find the respective numbers of
boys and girls in the class

2.
The mean age of all players in a football team is 21. If the35-year old
coach and 51-year old manage are included, the mean age if the team increases by 2. Find the total numbers of football players in the team

唔該哂

更新1:

請列埋條式 thz!

更新2:

thz 我總有一條唔識 A test paper consists of 20 multiple choice questions with equal score. It is known that the mean score of S3A students is 28 and the mean of the number of their correct answer is 14 a) find the score of each questions

更新3:

b) if the median of the numbers of correct answer is 16, find the median score of the students c) if the modes of the scores of the students is 34, find the mode of the number of correct answers

回答 (1)

Prof. Physics

2009-04-19 12:31 am

✔ 最佳答案

1. Let x be the number of boys in the class,

then (30 - x) is the number of girls in the class.

Whole class mean = 13.4

[21x + 9(30 - x)] / 30 = 13.4

x = 11

So, the number of boys in the class is 11

And the number of girls in the class is 30 - 11 = 19.

2. Let c be the total number of football players in the team

Now, the coach and the manager is included.

So, [21c + 35 + 51] / (c + 2) = 21 + 2

(21c + 86) / (c + 2) = 23

c = 20

So, the total numbers of football players in the team is 20.

2009-04-19 17:18:18 補充：
a. Score = 28 / 14 = 2

b. Median score = 16 X 2 = 32

c. Mode of no. of correct answers = 34 / 2 = 17

參考: Physics king

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