One pipe can fill a tank in 24 minutes, a second can fill it in 8 minutes, and a third can fill it in 12 minutes. If the tank is empty, how long will the three pipes, operating together, take to fill it? 4 4/5 minutes
4 minutes
1/6 minute

4 mins

Step-by-step explanation:

Tank 1: 24

Tank 2: 8

Tanks 3: 12

So you add them all up to equal the "work". which is one. Looks like this:

*** x/24 + x/8 + x/12 = 1 ***

multiply all by 24

x+3x+2x=24

add like terms

6x=24

divided by 6

x=4

So x=4 minutes.

:)

*** You could check by putting 4 into x by the * (stared) problem

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.

i would need to see the shape

step-by-step explanation: