two spheres, radii 7 and 4, are tangent to each other

[Love21]

Two spheres one with radius 7 and one with radius 4, are tangent to each other. if P is any point on one sphere and
Q is any point on the other sphere what is the maximum possible length of PQ ?

a) 7
b) 11
c) 14
d) 18
e) 22

Do you just multiply together or divide by something?

 

[pka]

Re: 2 spheres

Do you just multiply together or divide by something?

No you don't.
This is a concept question.
Visualize the two spheres touching at one point.
What is the maximum distance between two points, one on each sphere?
Think line through the centers.

 

[Love21]

Re: 2 spheres

I dont know if i understand...can you explain what i'm supposed to do?

 

[pka]

Re: 2 spheres

can you explain what i'm supposed to do?

Yes I can. You are supposed to think the problem through.
This is not an operation that one simply does. It is a thought problem.

 

[stapel]

I dont know if i understand...can you explain what i'm supposed to do?

The previous replies are exactly on mark: You need to review the definitions, and think about (and/or visualize in your head) what is being discussed. Then make a logical conclusion based on those definitions and the description.

If you are unable to do that (because you don't know what spheres are, or because you never learned about tangency, or whatever), then you'll need to back up and learn the necessary foundational material. For this, you would probably be best advised to hire a local qualified tutor, who can, in face-to-face sessions, help you review your text from the beginning, re-learning forgotten material, and filling in the various conceptual gaps in your knowledge.

Eliz.

 

[Loren]

It may be difficult to "visualize" so draw a sketch of two tangent circles with radii of 7 and 4. That should help you discover what you're after.