The center of a circle with a radius of three units is (1,1). Which of these points is on the circle?
A. (4,4)
B. (-2,1)
C. (-4,1)
D. (3,0)

Question

hero · Answer

Plot all the points on an xy plane or use the distance formula. Whichever point is a distance of 3 units from 1,1 is the correction solution.

anonymous · Answer

so A????

hero · Answer

wait a sec. Let me do it

hero · Answer

That's not 3 distance units. Did you use the distance formula?

hero · Answer

It's B

anonymous · Answer

well...plotting all the point and visualize everything will give you a feeling for the solution but the real way to do it is with the distance formula...which i cant recall...but A is a trap!

hero · Answer

Actually hat, the quickest way is to plot the points on an xy plane. That's why I know the answer is B

anonymous · Answer

yes i would go with  B as well...just a huntch

hero · Answer

Distance Formula takes longer, thats why I suggested plotting on xy plane first.

anonymous · Answer

distance formula takes longer but if u dont have designing tools around you distance formula can be a lot faster

mathmate · Answer

Also check visually points that line up with the centre, like (*,1), or (1,*).  The distance formula reduces to the difference.  B is such a case.  
However, we don't always get lucky this way.

hero · Answer

I don't consider graph paper a "designing tool"

hero · Answer

By default, if you're taking a math class, you should have graph paper handy