Question 325264
Jim can fill a pool carrying buckets of water in 30 minutes. Sue can do the same job in 45 minutes. Tony can do the same job in 1 ½ hours. How quickly can all three fill the pool together? 
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Hint:
Jim does 1/30 of the pool per minute.
Sue does 1/45 per minute.
Tony does 1/90 per minute.
Add those up, go from there.