One pipe fills a storage pool in 20 hours. a second pipe fills the same pool in 15 hours. when a third pipe is added and all three are used to fill the pool, it takes only 6 hours. find how long it takes the third pipe to do the job.

We work in rates per hour so we have the equation:-

1/20 + 1/15 + 1/x = 1/6 where x is the time for the third pipe

1/x = 1/6 - 1/15 - 1/20 = 1/20

so x = 20

The answer is 20 hours.

the polynomial is a perfect square trinomial of the form a^2-2ab+b^2:

option a. true

step-by-step explanation:

9x^2-12x+4

comparing with the form a^2-2ab+b^2

1.) a^2=9x^2

solving for a: square root both sides of the equation:

sqrt(a^2)=sqrt(9x^2)

a=sqrt(9) sqrt(x^2)

a=3x

2.) b^2=4

solving for b: square root both sides of the equation:

sqrt(b^2)=sqrt(4)

b=2

to be a perfet square trinomial 2ab must be equal to 12x. let's check:

2ab = 2 (3x) (2)

2ab = 12x

correct

i have not got your picture clearly so see it once again