## nasryn Group Title Oil spilled from a ruptured tanker is spreading in a circular pattern. If the radius of the circle is increasing at the constant rate of 1.5 feet per second, how fast is the area of the spill increasing when the radius of the spill is 42 feet? one year ago one year ago

1. goformit100 Group Title

use speed time formula...

2. nasryn Group Title

I've never heard of that.

3. satellite73 Group Title

related rates right?

4. nasryn Group Title

Yeah, related rates.

5. satellite73 Group Title

$$A=\pi r^2$$ and so $$A'=2\pi rr'$$

6. satellite73 Group Title

you are told $$r'=1.5$$ and $$r=42$$ plug in the numbers and get $$A'$$ in one step

7. nasryn Group Title

wow, that was easy. I'm terrible at these.

8. goformit100 Group Title

@bloodrain

9. satellite73 Group Title

yeah, i have to admit that one was real easy they get harder

10. nasryn Group Title

:(

11. satellite73 Group Title

well only the formulas get harder to figure out, i am willing to bet that you knew the formula for the area of a circle

12. nasryn Group Title

yeah, I was just thinking like A=pi(r^t/1.5)^2 then I was super confused

13. nasryn Group Title

That made absolutely no sense to me.

14. Dido525 Group Title

The minute hand on a watch is 8mm long and the hour hand is 4 mm long. How fast is the distance between the tips of the hands changing at one o'clock? THat's the hardest one I have done myself.