Answer: 600
Step-by-step explanation:
Given : Sue planted 4 times as many apple seeds as she planted orange seeds. 15 percent of the apple seeds grew into trees, and 10 percent of the orange seeds grew into trees
Let x be the number of apply seeds and y be the number of orange seeds , the we have the following equations:-
[tex]x=4y[/tex] (1)
[tex]0.15x+0.10y=420[/tex] (2)
Put x= 4y in (2), we get
[tex]0.15(4y)+0.10y=420[/tex]
[tex]0.60y+0.10y=420[/tex]
[tex]0.70y=420[/tex]
Divide both sides by 0.70.
[tex]y=600[/tex]
Hence, Sue planted 600 orange seeds.