Hello All,

My daughter, Natasha, is in 4th grade. She had the following homework question about rays that confused us:

Name as many rays as you can in the figure below.


<---.----.--------------------------.-----.------.------> (line not dotted on homework sheet)
      L   M                              N     O      P

She named:
--> --> --> --> --> -->  --> --> -->  --> -->  --> -->  --> -->  --> --> --> -->  -->
LM, LN, LO, LP, ML, MN, MO, MP, NL, NM, NO, NP, OP, ON, OM, OL, PO, PN, PM, PL

In grading the answer all of the above were crossed out as incorrect except:
--> --> --> -->  --> --> -->
LP, ML, MP, NL, NP, OP, OL
                                          -->                                                       -->
We can see that, for example, LN (one of those crossed out) is included in LP, but does that mean that there is not a ray
           -->
named LN?

Thanks so much for your help!

Natasha, 4th grade and mom

Hi,

In geometry a ray or half line starts at a point and go indefinitely in some direction. The term probably comes from a light ray. To specify a ray you need two points, a starting point and a second point to indicate the direction. In your example above

-->
LN

is the ray that starts at L and goes to the right. The ray

-->
LP

also starts at L and goes to the right. They are exactly the same ray, they are just described differently. In the problem you were given here you can describe 4 rays that go to the right, one starts at L, the second at M, the third at N and the fourth at O. There is a ray that starts at P and goes to the right but you have no point to the right of P to allow you to specify "to the right".

There are also 4 rays you can describe that go to the left. What I don't understand is that in the answer given there is no ray that starts at P and goes to the left. You might call it

-->
PO

or

-->
PN

or

-->
PM

or

-->
PL

but it should be there.

I hope this helps,
Penny