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Several months ago, Deven bought two plants. The two plants had the same height at the time when they were purchased. Ever since then, Plant A grew 10  centimeters every month. Plant B grew 1 centimeter in the first month after its purchase, 2 centimeters in the following month, and generally grew n centimeters in the nth month after its purchase. Deven finds out today that the two plants have the same height again. How many months ago did he buy the two plants?

 

Thanks to anyone who can solve this! :)

 Jan 13, 2019
 #1
avatar+533 
+2

after x months, plant a grows 10x centimeters, and after x months, plant b grows x(x+1)/2 because of the formula for triangluar numbers. this means those two are equal, so 10x=x(x+1)/2 or 20x=x(x+1), which means 20=x+1 so x=19.

 

HOPE THIS HELPED!

 Jan 13, 2019
 #2
avatar+143 
+2

Wow! That was fast! And yes it did help a lot! Thanks!!

noobieatmath  Jan 13, 2019
 #3
avatar+533 
+2

yw!!

 Jan 13, 2019

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