# Rates of change: The rate of change of the area of a triangle. Is my answer right?

my question is... is this answer correct? for the last step. WOULDNT you multiply 10x by .5 and 12 by .2? the opposite of what this answer is? Itsays BASE is 10 in and BASE chagnges at .5 in per second
problem:
i45.tinypic.com/xknbci.png
i50.tinypic.com/2qcnsyv.jpg

this is what i get...

i50.tinypic.com/124cxgy.jpg

SammyS
Staff Emeritus
Homework Helper
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my question is... is this answer correct? for the last step. WOULDN'T you multiply 10[STRIKE]x[/STRIKE] by .5 and 12 by .2? the opposite of what this answer is? It says BASE is 10 in and BASE changes at .5 in per second
problem:
i45.tinypic.com/xknbci.png
i50.tinypic.com/2qcnsyv.jpg

this is what i get...

i50.tinypic.com/124cxgy.jpg
Hello indigo1. Welcome to PF !

Why would you want to multiply the base by the rate of change of the base? Even your working has $\displaystyle b\frac{dh}{dt}$ and $\displaystyle h\frac{db}{dt}\ .$

dh/dt is -0.2 in/sec and db/dt is 0.5 in/sec !

BTW: Below are your images, displayed so others can see them.

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