math. problems

1. which set is closed under division
(1) 1 (2) counting number (3) intergers (4) whole number
ANSWER: 1
Since 1/1=1 So, this set is closed under division
Other sets should not be closed under division
for example 6/4=1.5 is not an counting number or interger
2. when kimberly bought her new car, she found that there were 72 different ways her car could be equipped. her choices included 4 choices of engine, 3 choices od transmission, if her only other choice was color, how many choices of color did she have?
(1) 6 (20 12 (3) 60 (4) 65
ANSWER:1
Since 72/(4*3)=6
3. a company manufactures bicycles and skateboards. the daily production of bicycles of the company cannot exceed 10, and its daily production of skateboards must be less than or equal to 12.
3. a company manufactures bicycles and skateboards. the daily production of bicycles of the company cannot exceed 10, and its daily production of skateboards must be less than or equal to 12. The combination number of bicycles and skateboards cannot be more than 16. if x represents the number of bicycles , and y represents the number of skateboards. make a graph that represents the products that the company can produce daily.
condition:
1 x>=0
2 y>=0
3 x<=10
4 y<=12
5 x+y<=16
6 x,y integers
Then you draw all the lines on the graph, the point in the region which is combined by these lines is the products that the company can produce daily.

2007-02-24 06:21:47 補充：
第3題我指的lines是x=0, y=0, x=10, y=12, x+y=16

2007-02-24 06:35:46 補充：
which is combined by these inequalities