If Andy and Billy work together, they can complete a project in 3.6 hours. If each of them works individually, Andy needs 3 hours less than Billy to complete the project. How long does Billy take to complete the project on his own?

Question

dmezzullo · Answer

$${\rm Time =}\dfrac{ab}{a + b}$$U have $a = b - 3$

dmezzullo · Answer

$$\dfrac{b(b - 3)}{b + b - 3} = 3.6$$solve?

anonymous · Answer

b=1.2 or b=9 ?

hartnn · Answer

those are correct values of b.

hartnn · Answer

which value of 'b' you can eliminate ?

dmezzullo · Answer

HINT: $a = b -3$ but one of the $a$'s will be negative.

anonymous · Answer

a=9-3=6
a=1.2-3=-1.8(rej.)

anonymous · Answer

so i should get the answer a=6 and b=9. Therefore, Billy takes 9 hours to complete the project on his own. Right?

dmezzullo · Answer

thats right

dmezzullo · Answer

yes!

anonymous · Answer

thanks

hartnn · Answer

$\huge \color{green}\checkmark$