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A work crew has a new pump and an old pump. The new pump can fill a tank in 5 hours, and the old pump can fill the same tank in 7 hours. Write and solve an equation for the time it will take both pumps to fill one tank if the pumps are used together

Respuesta :

cello10
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new pump rate:: [tex] \frac{1}{5} [/tex] job/hr
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old pump rate:: [tex] \frac{1}{7} [/tex] job/hr
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together rate:: [tex] \frac{1}{x} [/tex] job/hr
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Equation:
rate + rate = together rate
[tex] \frac{1}{5} [/tex] + [tex] \frac{1}{7} [/tex] = [tex] \frac{1}{x} [/tex]7x + 5x = 35
12x = 35
x = [tex] \frac{35}{12} [/tex] = 2 [tex] \frac{11}{12} [/tex] hr = 2hr 55 min (time to do the job together)

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