Question 150456
if my son worked on the garden by himself it would take him 4 hours longer to weed the garden than his grandfather took. However, if he worked with my father-in-law, he worked twice as fast. The formula 
t(t+4)/3t+4 represents how long it took for both of them to weed the whole garden working together. 
Using the formula t(t+4)/3t+4, How long would it take the son alone,if it took an hour and a quarter for them to weed the garden together? 
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Find "t":
[t(t+4)/(3t+4)] = 5/4 hr
[t^2+4t]/[3t+4] = 5/4
Cross-multiply to get:
4t^2+16t = 15t+20
4t^2 + 11t - 20 = 0
4t^2 + 16t-5t -20 = 0
4t(t+4) + 5(t+4) = 0
(t+4)(4t+5) = 0
t = -4 or t = -5/4
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Comment: These answers are unrealistic.
Is the formula correct?  Shoud it be [t(t+4)/3t] + 4 ?
or something else?
Cheers,
Stan H.