This is easier for me to think through in words rather than have to derive some formula first.
If Sam and Elsie were working together for an hour, then they were half done, since either of them could have done the job in 4 hours, which means those two together would take 2 hours to finish.
It would have taken them one more hour to finish. The fact that it now took only thirty minutes means that Gregory worked as fast as Sam and Elsie combined.
The answer is therefore one hour.
Sam Bordner can dig his garden in 4 hours end Elsie Bordner takes the same amount of time. After working together for an hour, their son Gregory helps them finish in just 30 minutes. How long would it have taken gregory to dig the garden by himself?
Can someone help me form an equation?
1 answer
5 answers