Question

Determine which lines are parallel and which are not parallel. Explain your reasoning.

Answer 1

Answer:

If M and N are parallel, then the correspondent angles generated by the intersection with line R (or line S) should be equal.

So, if M and N are parallel, we should get that angles 2 and angle 4 are equal, as both of these are on the fourth quadrant of the intersection with the same line.

Similarly, if R and S are parallel, then correspondent angles generated by the intersection with line M (or line N) should be equal, this means that:

angle 3 and angle 7 should be equal.

Also remember that if we have two lines intersecting, generating 4 angles, any pair of two adjacent angles will always add to 180°.

Here we have two cases:

1)  m∠3=69°, m∠7=71°

Here we can see that:

m∠3 ≠ m∠7

Thus, lines  R and S are not parallel.

And here we do not have any information on the angles 1, 2, 5, and 6, so we can't compare the angles generated by line N with the ones generated by line M, so we can not know if lines N and M are parallel or not.

2) Now we have that:

m∠3=76°  , m∠8=114°

Notice that angle 8 and angle 7 are adjacent, then we have that:

∠7 + ∠8 = 180°

And we know that:

∠8 = 114°

Then:

∠7 + 114° = 180°

∠7 = 180° - 114° = 76°

Then we have:

∠7 = ∠3

From this we can conclude that lines R and S are parallel.

(again, we can not do anything with lines N and M)