Question 371905
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Hi,
Let x represent the time in minutes it takes all three to fill the pool
Per minute is the Equalizer***
1/30 + 1/45 + 1/90 = 1/x  Multiplying all terms by 90x so as all denominators= 1
3x + 2x + x = 90
6x = 90
x = 15 minutes, the time it takes all three to fill the pool

chaecking our answer
3/90 + 2/90 + 1/90 = 6/90 = 1/15