Question

Sarah and Billy built their own tree houses that were the same size. It took Billy 5 hours to build his treehouse and Sarah took 8 hours. How much time would it take for Sarah and Billy built a treehouse together?

Write a rational expression based on the word problem.

Answer 1

@agent0smith

Answer 2

I do these like parallel resistor problems in physics.\[\Large \frac{ 1 }{ t }=\frac{ 1 }{ 5 }+\frac{ 1 }{8 }\]Solve for t.

Answer 3

ohh ok

Answer 4

(1/5 + 1/8)(t) = 1

Answer 5

cross multiply correct?

Answer 6

A tip or shortcut, when two are involved, use product over sum:
(5)(8)/(5 + 8) or 40/13

Answer 7

yep

Answer 8

could someone walk me through how to solve for t?

Answer 9

t = 1/ (1/5 + 1/8)

Answer 10

what? can you use the equation editor

Answer 11

\[t= \frac{1 }{ 1/5 + 1/8 }\]

Answer 12

hmm next step?

Answer 13

@radar @RadEn

Answer 14

I use product over sum 40/13, but if you insist on using the old fashion way, the common denominator would be 40