<span>Rate of pump A: 1/8 of a pool per hour
Rate of pump B: 1/9 of a pool per hour
Combined rate: 1/8+1/9 = 17/72 +1/9 = 25/72
So if they work together, the two pumps have a combined rate of 25/72 of a pool per hour (i.e in one hour, the two pumps will empty 25/72 of the pool)
</span><span>But we want to empty ONE pool (not 25/72 of one). So we need to multiply 25/72 by some number x to get 1.
</span>
<span>Now solve for x
x=2.88
</span><span>It will take the two pumps 2.88 hours to empty the pool.
2 hours 52 minutes 50 seconds</span>
If you know that
, then you know right away

###
Otherwise, you can derive the same result. Let
, so that
.
is bounded, so we know
. For these values of
, we always have
.
So, recalling the Pythagorean theorem, we find

Then

as expected.
First you have to find a common denominator which would be 24.
5/6 = 20/24
7/8 = 21/24
5/8 = 15/24
So your final answer would be 7 over 8.
Answer:
C, the 3rd one
Hope this helped! Have a great day!
<span>(6+8)/2 = 14/2 = 7 hope this helps
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