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1.If the length,in inches,of all three sides of a triangle a

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1.If the length,in inches,of all three sides of a triangle are integers,and one side is 7 inches long,what is the least possible perimeter of the triangle in inches?
A.9
B.10
C.15
D.21
E.24
可是为什么?
2.In your job at a company that makes bowling balls,you are doing a quick check of how much plastic resin has been used this week by the machine that molds the balls.Each ball is sphere with a radius of 4 inches ( the finger holes are drilled out after the ball has been molded.) Production records show that 1,200 balls were made this week.Ignoring waste,about how many cubic feet of resin were used in the machine this week?
答案是186 为什么
3.Two boys can paint a fence in 5 hours.How many hours would it take for 3 boys to paint the same fence?
答案是3⅓ 为什么
4.Given circle O below
m∠BAC=x and m∠BOC=y,m⌒BC= 70
Find x+y
答案是105
所有题求详解 会有分的、
1、one side is 7,and the sum of the other 2 sides must be > 7,that is the smallest sum is 8.
so the least perimeter will be 7+8=15
2、the sphere volume= (4/3)π r^3
one ball's volume=(4/3)*3.14*4^3=268 cube inch
1200 balls=268*1200=321600 cube inch
and 1 feet=12 inches
so 321600 cube inch=321600/(12^3)=186 cube feet
3、two boys can paint a fence in 5 hours,
so 1 boy spends 1 hour on 1/10 of the task
therefor,it will take 1 hour for 3 boys to do 3/10 of the task
so,it will take 10/3 hours for 3 boys to finish the job
4、m⌒BC=m∠BOC=y=70
and m∠BAC=x=m∠BOC/2=y/2=35
(there is a theorem says that a circumference angle equals to a half of the central angle at the same arc)
so,x+y=70+35=105