Respuesta :
We have to find out the number of trees planted per unit rate of time.
Kyla can plant 300 trees in 1 hour, so she can plant 300 trees in 3600 seconds. This implies that she can plant
[tex]\dfrac{300}{3600}=\dfrac{1}{12}[/tex]
trees per second.
On the other hand, Mia can plant 1 tree in 13 seconds, so she can plant
[tex]\dfrac{1}{13}[/tex]
trees per second.
Working together they can plant
[tex]\dfrac{1}{12}+\dfrac{1}{13}=\dfrac{25}{156}[/tex]
trees per second, i.e. it takes them 156/25 seconds to plant a tree.
We conclude that they plany 100 trees in
[tex]\dfrac{156}{25}\cdot 100=156\cdot 4=624[/tex]
seconds
