00:01
So the theme in this problem is basically distance equals rate times time.
00:06
The difference, though, is that if you're from the finish line, that you want to start out with a negative distance.
00:17
Or maybe you want to do, how about this? i'll just give you the answer.
00:22
For the first one, is f of t is we are 2 ,000 meters, but.
00:31
We're moving closer to the finish line.
00:34
So you want to subtract off the, let's see, five meters per second.
00:39
So five times t.
00:40
And you can double check that this is the right answer because if you plug in one second in for t, you'd be 1995 away.
00:51
And it should make sense.
00:53
So if you're asked to solve for letter b, you just set this equal to zero by the time they finish.
01:01
And what i would do is subtract, or sorry, add 5t to the right side and divide by 5.
01:08
And i believe this answer would be t would equal 400.
01:14
You double check 2 ,000 divided by 5.
01:18
So it would take 400 seconds.
01:23
I don't know if you need to convert that, but that's the units that we're looking for.
01:28
So the next one is a little bit trickier because this thing, it doesn't say when the hair started moving.
01:43
It just said that gave the first one a 530 meter head start.
01:54
So for, i guess, several seconds, i guess the hair is not moving at all.
02:06
And when does the hair start moving is after, so i don't know if you're allowed to make a piecewise function in this, but for a while, the hair is not moving from zero seconds all the way until what i would do is figure out when the tortoise gets to 530.
02:30
So 2 ,000 minus 5t is equal to 530...