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
--> --> --> --> --> --> --> --> --> --> --> --> --> --> --> --> --> --> --> -->
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
Thanks so much for your help!
Natasha, 4th grade and mom
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
is the ray that starts at L and goes to the right. The ray
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
but it should be there.
I hope this helps,