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If Rhonda can type a 1000 word report in 4 hours, and while her friend Betty types on the same report, they finish it in 3 hours, how long would it take Betty to type the report by herself

Respuesta :

R * 4 = 1000; R = 1000 / 4 = 250
(R + B) * 3 = 1000
3R + 3B = 1000, 
3B = 1000 - 3R = 1000 - 750 = 250
B = 250/3 

t(B) = 1000 / (250/3) = 12 hours


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