A few days ago
Anonymous

Triangle Rate Problem- Please Help! =/?

The altitude of a triangle is increasing at a rate of 1.000 centimeters/minute while the area of the triangle is increasing at a rate of 1.000 square centimeters/minute. At what rate is the base of the triangle changing when the altitude is 7.500 centimeters and the area is 90.000 square centimeters?

——

Please show steps and reasoning.

Thanks for any help, hints, or suggestions. =)

Top 1 Answers
A few days ago
Anonymous

Favorite Answer

Let the base be b, the height (= length of altitude) be h and the area be A. These quantities can all be expressed as functions of time.

A = bh / 2 ………(1)

Differentiating with respect to time, and using the product rule:

dA/dt = (b dh/dt + h db/dt) / 2

2 dA/dt = b dh/dt + h db/dt

db/dt = (2 dA/dt – b dh/dt ) / h ……..(2)

dh/dt = 1000 cm / min

dA/dt = 1000 cm^2 / min

h = 7500 cm

A = 90000 cm^2

From (1)

b = 2A / h

= 2 * 90000 / 7500 cm

b = 24 cm.

Substituting these values in (2):

db/dt = (2*1000 – 24*1000) / 7500

= -220 / 75

= -2.93cm / min.

0