gdshamain wrote:When a certain tree was first plated it was 4 feet tall, and the height of the tree increased by a constant amount each year for the next 6 years. 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 feet did the height of the tree increase per year?
A) 3/10
B) 2/5
C) 1/2
D) 2/3
E) 6/5
Let's try plugging in the answers, starting from (C) as usual.
If the height of the tree increases @ ½ feet per year, then at the end of the 4th year, it would be 6 feet, and at the end of the 6th year, it would 7 feet. We can justify that 7 is not 1/5 taller than 6, it's even less in fact. This is because we picked a choice that is too small to make it true.
Eliminate (C) and the smaller choices, (A) and (B).
Take one more attempt, say try (D).
If the height of the tree increases @ 2/3 feet per year, then at the end of the 4th year, it would be 20/3 feet, and at the end of the 6th year, it would 24/3 feet. We can justify that 24/3 is 1/5 taller than 20/3, hence [spoiler]
(D)[/spoiler] is the right choice, take it!
