



 
Hi David, Della can scrape the ship in 10 hours so she scrapes at the rate of one tenth of a ship per hour. She works for 3 hours so she scraped three tenths of the ship. Della can scrape a ship in 10 hours and Don can scrape a ship in 15 hours. If they work together how long does it take to scrape seven tenths of a ship? Penny  


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