Posted by **Anonymous** on Sunday, October 14, 2007 at 1:37am.

A 15 ft ladder leans against a wall. The bottom of the ladder is 3 ft from the wall at time t=0 and slides away from the wall at a rate of 3ft/sec.

Find the velocity of the top of the ladder at time t=3.

- Math -
**Reiny**, Sunday, October 14, 2007 at 8:47am
Let the foot of the ladder be x feet from the wall

let the height of the ladder be y feet

then x^2 + y^2 = 225

differentiate with respect to t, this is a "related rate problem"

2x dx/dt + 2y dy/dt = 0 (1)

when t=3 sec,

x = 9 feet (you knew the rate)

then 81+y^2=225

y=12 feet

sub x=9, y=12, dx/dt = 3 into (1) and solve for dy/dt

I got dy/dt = -9/4 ft/sec

(the negative value shows that y was decreasing at 9/4 ft/sec at that instant)

- Math -
**Anonymous**, Wednesday, September 7, 2011 at 3:42pm
a building is 3ft. from a 8ft. fence that surround propert a worker wants to wash a window in the building 13ft. from the ground. he will need what size ft. ladder

## Answer This Question

## Related Questions

- Calculus - A 18 ft ladder leans against a wall. The bottom of the ladder is 4 ft...
- Calculus - A 15 ft ladder leans against a wall. The bottom of the ladder is 4 ...
- calculus - A 15-ft ladder rests against a vertical wall. If the top of the ...
- Calculus - 1a. 15 ft ladder is placed against a vertical wall. the bottom of the...
- AP calc bc - A 25-ft ladder rests against a vertical wall. If the bottom of the ...
- calculus - A 25-ft ladder rests against a vertical wall. If the bottom of the ...
- calculus - a ladder 6 feet long leans against a vertical building. the bottom of...
- caculus - A 10-ft ladder rests against a vertical wall. If the bottom of the ...
- calculus 1 - a ladder 20 ft. long rests against a vertical wall.If the bottom of...
- Calculas - A 13ft ladder is placed against a verticle wall. Suppose the bottom ...

More Related Questions