<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>
1
Hold your hands out in front of you with your palms facing up. Each of your ten fingers represent a number. Moving from your left thumb to your right thumb, count out the numbers from one to ten.
2
Point the finger you want to multiply by nine down towards your body. For example, if you want to solve (9x3) you will want to hold down your middle finger on your left hand. The middle finger represents the number three because, if you count your fingers from one to ten beginning with your left thumb, your middle finger is the third finger.
3
Solve the problem by counting fingers to the left and right. First count the fingers to the left of your bent finger - in this case there should be two. Next count the fingers to the right of your bent finger - in this case there should be seven. The first digit of the answer is 2 and the second digit is 7. The answer is 27![1]
The answer is C. Good luck
