Another question from OG.

[mschling52]

I think the answer is D - 2/3.

Let x be the amount the tree grows each year. We are given that

4+6x = (4+4x)+(1/5)(4+4x)
4+6x = (6/5)(4+4x)

(height at end of 6th year = height at end of 4th year + 1/5 of the height at the end of the 4th year)

We can then solve for x,

4+6x = (24/5) + (24/5)x
(6/5)x = 4/5
x = (4/5)*(5/6) = (4/6) = (2/3)