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# Co linear points Watch

1. According to the mark scheme the answer is B. I got C but I don't think I full understand the question.

PQ : PR is equal to 3:5 but it asks for Q : PR and PR is not written as a vector? help
2. (Original post by Feynboy)

According to the mark scheme the answer is B. I got C but I don't think I full understand the question.

PQ : PR is equal to 3:5 but it asks for Q : PR and PR is not written as a vector? help
You can find the vector PR because you can find R since you're given the vector from Q to R, and the point Q itself.
3. (Original post by RDKGames)
You can find the vector PR because you can find R since you're given the vector from Q to R, and the point Q itself.
Find R by saying QR = R - Q

Find PR by saying PR = R - P as we now know R and were given P.

But they don't equate to 3:2 for Q : PR is what I'm doing right
4. (Original post by Feynboy)
Find R by saying QR = R - Q

Find PR by saying PR = R - P as we now know R and were given P.

But they don't equate to 3:2 for Q : PR is what I'm doing right
Okay I think you're thinking it about it the wrong way.

Find PR and get its magnitude.

Find PQ and get its magnitude.

You should find that, with magnitude concerned, PQ + QR = PR and you can find QR since you know the other two. Things should cancel and you'd be left with 3+2=5; therefore Q, being between P and R, would split the overall length PR into 3:2

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