Question 17697: Hello, my question is a pre-algebra one and I have tried to work it out like this, but first of all the question is: A factory manufactured 30,000 tennis blls in 2 weeks. Out of every 1000 tennis balls produced 15 defective. What proportion can be used to find the number of tennis balls, t, that were judged to be defective in the 2 weeks?
This is how I worked it out: 30,000 tennis balls = 1,000 tennis balls
___________________ __________________
15 defective t
= 15(1,000)
= 15,000 = 30,000(t)
__________ = ___________
30,000 = 30,000t
t= 0.5
Could you please let me know if I missed something or if I worked it correctly? Thank you, Karissa
Answer by xcentaur(357)   (Show Source):
You can put this solution on YOUR website! Lets check,
Now let the proportion of defective balls be t
out of every thousand,15 are defective.
Hence out of 30000,t are defective
1000 : 15 = 30000 : t
That is the proportion you would require.
To put it more clearly,
15 is to 1000, what 't' is to 30000
t=30000*15/1000=30*15=450 defective out of 30,000
Logically,if 15 are defective out of 1000 then out of 30,000 there have to be more defective,so the value of t you obtained as 0.5 is incorrect.Try the sum again and keep practising,I'm sure you'll get it.
Hope this helps,
Prabhat
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