When a certain tree was first planted

[lionheart]

When a certain tree was first planted, it was 4ft tall, and the height of the tree increased by a constant amount each year for the next 6 yrs. At the end of the 6th year, the tree was 1/5 taller than it was at the end of the 4th year. By how many ft. did the height of the tree increase each year?

[Guest]

Do a quick search, it's been answered before.

mdh

[GMAT700]

0 time = 4 (feet)
yr 1 = 4 + n(constant)
yr 2 = (4+n) + n = 4+2n
yr 3 = 4+3n
yr 4 + 4+4n
yr 5 = 4+5n
yr 6 + 4+6n

4+6n = 4+4n + 1/5

2n = 1/5
n= 1/10, which should be your answer.

check: 6n - 4n = 6/10-4/10 = 2/10 = 1/5 taller in the 6th year than it was at the end of the 4th year, so this works out.

[RonPurewal]

http://www.manhattangmat.com/forums/whe ... -t646.html