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As Old As The Trees

Category:	Math
Submitted By:	TRILLIONAIRE
Fun:	(2.26)
Difficulty:	(2.14)

During its first year a species of tree reaches a height of 7cm. It continues to grow for another 9 years attaining its maximum height at 10 years of age. Each year it continues to grow at the rate of double the previous year's height. At what age will the tree be half its maximum height?

Note: The tree grows at a constant speed throughout the year.

Answer:

9.25 years

Every year the tree is 3 times as high as it was the previous year.

That means if it is x high, it will gain 2x throughout the year, totaling 3x at the end. We want to find when it is 1.5x.

If it gains 2x every year, it will gain x every six months, or .5x every 3 months. Also stated as .5x every quarter of a year or .25 years.

So .25 of the way through the year, it will be half the height it will be at the end of the year.

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Comments on this teaser


Posted by agal1977	04/04/08
:D A wonderful Math teaser. It made me think and I really enjoyed it.

Posted by ebraham	04/06/08
A good math brain teaser! Thanks For A Great Teaser TRILLIONARE!

Posted by sweetmama	04/07/08
My head officially hurts, lol jk! Nice teaser!

Posted by SSVillalobos	04/14/08
I liked this one, but was off by 1/4 year. Hrmph. :)