Question

final exam today. I cannot remember how to answer these kinds of questions! Someone help remind me?

Bubba can mow the lawn in 3 hours. Pierre takes 10 hours. How long does it take them to mow the lawn together?

Answer 1

save time on the exam, go right to the answer
\[\frac{3\times 10}{3+10}\] then compute
it takes less than a minute

Answer 2

we can work out the long involved process for solving this, but this is the answer you will get
only thing left to do is arithmetic
\[\frac{3\times 10}{3+10}=\frac{30}{13}\]

Answer 3

or if you want the formula.. \[\huge \frac tx + \frac ty = 1\]
where t is the total time working together
x is the time it takes for an individual to finish the job alone
y is the time it takes for another individual to finish the job alone

Answer 4

leaving you with more times for other exam questions

Answer 5

\[\huge (\frac 1x + \frac 1y)t = 1\]
\[\huge(\frac{x+y}{xy})t=1\]
\[\huge t=\frac{xy}{x+y}\] as promised

Answer 6

you are amazing! thank you to both of you!