Answer:
2 bottles
Step-by-step explanation:
The 15 trees will need ...
(15 trees)×(10.5 fl oz/tree) = 157.5 fl oz
This is about ...
(157.5 fl oz)/(33.814 fl oz/L) ≈ 4.66 L
This is just slightly more than the quantity available in 1 bottle. It amounts to ...
4.66 L/(4.1 L/bottle) ≈ 1.14 bottles
We assume that only whole bottles can be purchased, and that we do not have an inventory of fertilizer on hand.
2 bottles are needed to fertilize 15 trees