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Integration problem

  • #1

Homework Statement

the lifetime of a machine part has a continuous distribution on the interval(0,40) with probability density function f, where f(x) is proportional to (10 + x)^(-2) Calculate the probability that the lifetime of the machine part is less than 6.



Homework Equations





The Attempt at a Solution

My book says that since f(x) is proportional to (10 + x), f(x)=k(10+x)^(-2). My question is why we need to put the k in the equation? Is it merely because the question says that they're proportional and so we need to set up that integration to find by how much they're proportional?
 

Answers and Replies

  • #2
ideasrule
Homework Helper
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Yes.
 

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