F3數學第一課 - Ans.fyi 參考答案

F3數學第一課

Kwok hei

2012-09-10 12:02 am

F3數學第一課 Linear Inequalities in One Unknown
有兩條數不會做
文字題,列式順便解釋一下謝謝
1.For two consecutive multiples of 3,5 times the larger number is not less than 2 times the smaller number plus 45.Find the minimum values of these two numbers.
2.The alcohol contents by volume of two drinks are given as follows:
Drink A alcohol content:15%
Drink B alcohol content:8%
At least how much drink A should be added to 3L of drink B,so that there is not less than 10% of alcohol by volume in the mixture?

回答 (1)

angela

2012-09-10 1:39 am

✔ 最佳答案

1.Let x be the smaller number
5(x+3)≥2x+45 <<<<2個multiples相差3
3x≥30
x≥10
Therefore,the minimum value of the two numbers is 12 and 15.
(因為10之後最細既multiple of 3係12)

2.Let y L be the volume of A
[0.15y+3(0.08)]/(y+3) X 100% ≥ 10% <<0.15=15%, 0.08=8%
0.15y+0.24 ≥ 0.1y+0.3
0.05y ≥ 0.06
y ≥ 1.2
Therefore, at least 1.2L of drink A should be added to 3L of drink B

參考: 自己

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