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A8

Work with coordinates in all four quadrants

Coordinates

Worked answers, methods and verified real exam appearances for A8 on Edexcel GCSE Maths 1MA1.

Explanation

  • A coordinate (x,y)(x,y) gives horizontal position first and vertical position second. Positive xx is right, negative xx is left, positive yy is up and negative yy is down.
  • The signs identify the quadrant, numbered anticlockwise from the top right.
  • Find a displacement by subtracting starting coordinates from ending coordinates.
  • Find a midpoint by averaging the two xx-coordinates and separately averaging the two yy-coordinates.
  • Examiners expect coordinate order and negative signs to be preserved, with the two component calculations shown clearly.
The four coordinate quadrants and the signs of (x,y)(x,y) in each.

Worked example

Find the midpoint of the segment joining (5,2)(-5,2) and (3,4)(3,-4).

  1. 1.Average the xx-coordinates: 5+32=1\dfrac{-5+3}{2}=-1.
  2. 2.Average the yy-coordinates: 2+(4)2=1\dfrac{2+(-4)}{2}=-1.
  3. 3.Write the coordinates in (x,y)(x,y) order.

Answer: (1,1)(-1,-1).

Common mistakes

  • Don't write the vertical coordinate first and swap (x,y)(x,y).
  • Don't lose a negative sign when averaging coordinates.
  • Don't find half the coordinate differences but forget to add them to an endpoint.

Exam tip

Write the midpoint as two separate averages before combining them into one ordered pair.

Worked practice

Q1
Tier 1 · Easy

1

State the quadrant containing the point (4,3)(-4,3).

(1)

(Total for Question 1 is 1 mark)

Mark scheme

Mark scheme for question 1
QuestionAnswerMarkMark scheme
1
  • Quadrant II
1The xx-coordinate is negative and the yy-coordinate is positive, which places the point in quadrant II.
Q2
Tier 3 · Hard

2

The point PP divides the line segment from A(6,5)A(-6,5) to B(4,5)B(4,-5) in the ratio AP:PB=3:2AP:PB=3:2. Find the coordinates of PP.

(3)

(Total for Question 2 is 3 marks)

Mark scheme

Mark scheme for question 2
QuestionAnswerMarkMark scheme
2
  • P=(0,1)P=(0,-1)
3The vector from AA to BB is (10,10)(10,-10). Since APAP is 3/53/5 of the whole segment, AP=(6,6)AP=(6,-6). Adding this to AA gives P=(6,5)+(6,6)=(0,1)P=(-6,5)+(6,-6)=(0,-1).
Q3
Tier 1 · Easy

3

The point (a,4)(a,-4) is in the bottom-left quadrant of the coordinate grid. Write down whether aa is positive or negative.

(1)

(Total for Question 3 is 1 mark)

Mark scheme

Mark scheme for question 3
QuestionAnswerMarkMark scheme
3
  • aa is negative (or a<0a<0)
1In the bottom-left quadrant, both coordinates are negative. The xx-coordinate is aa, so aa must be negative.
Q4
Tier 2 · Standard

4

A point moves from (4,1)(-4,-1) to (2,3)(2,3). Write down its horizontal displacement and its vertical displacement.

(2)

(Total for Question 4 is 2 marks)

Mark scheme

Mark scheme for question 4
QuestionAnswerMarkMark scheme
4
  • 66 units right
  • 44 units up
2For the horizontal displacement, 2(4)=62-(-4)=6, so it moves 66 units right. For the vertical displacement, 3(1)=43-(-1)=4, so it moves 44 units up.
Q5
Tier 3 · Hard

5

The midpoint of A(7,4)A(-7,4) and BB is M(2,1)M(-2,-1). Find the coordinates of BB.

(3)

(Total for Question 5 is 3 marks)

Mark scheme

Mark scheme for question 5
QuestionAnswerMarkMark scheme
5
  • B=(3,6)B=(3,-6)
3From AA to the midpoint, the change is (5,5)(5,-5). The same change takes the midpoint to BB, so B=(2+5,15)=(3,6)B=(-2+5,-1-5)=(3,-6).
Q6
Tier 2 · Standard

6

ABCDABCD is a rectangle whose vertices are named in order and whose sides are parallel to the coordinate axes. Three vertices are A(3,2)A(-3,2), B(5,2)B(5,2) and C(5,4)C(5,-4). Find the coordinates of DD and the perimeter of the rectangle.

(3)

(Total for Question 6 is 3 marks)

Mark scheme

Mark scheme for question 6
QuestionAnswerMarkMark scheme
6
  • D=(3,4)D=(-3,-4)
  • Perimeter =28=28 units
3Since ADAD is vertical, DD has the same xx-coordinate as AA. Since CDCD is horizontal, DD has the same yy-coordinate as CC, so D=(3,4)D=(-3,-4). The side lengths are 88 and 66, giving perimeter 2(8+6)=282(8+6)=28 units.
Q7
Tier 3 · Hard

7

MM is the midpoint of P(6,4)P(-6,4) and Q(8,2)Q(8,-2). Point RR is 33 units left and 55 units above MM. Find the coordinates of RR and write down the quadrant containing RR.

(3)

(Total for Question 7 is 3 marks)

Mark scheme

Mark scheme for question 7
QuestionAnswerMarkMark scheme
7
  • R=(2,6)R=(-2,6)
  • The top-left quadrant, where xx is negative and yy is positive.
3The midpoint is M=(6+82,422)=(1,1)M=\left(\dfrac{-6+8}{2},\dfrac{4-2}{2}\right)=(1,1). Moving 33 units left and 55 units up gives R=(13,1+5)=(2,6)R=(1-3,1+5)=(-2,6). A negative xx-coordinate and positive yy-coordinate place RR in the top-left quadrant.
Q8
Tier 3 · Hard

8

The points A(5,2)A(-5,2), B(1,7)B(1,7), C(6,1)C(6,-1) and DD occur consecutively around a parallelogram. Find the coordinates of DD. Check your answer by showing that the two diagonals have the same midpoint.

(4)

(Total for Question 8 is 4 marks)

Mark scheme

Mark scheme for question 8
QuestionAnswerMarkMark scheme
8
  • D=(0,6)D=(0,-6)
  • Both diagonal midpoints are (12,12)\left(\dfrac12,\dfrac12\right)
4For consecutively named vertices, AD=BC=(5,8)\overrightarrow{AD}=\overrightarrow{BC}=(5,-8). Hence D=(5,2)+(5,8)=(0,6)D=(-5,2)+(5,-8)=(0,-6). The midpoint of ACAC is (5+62,212)=(12,12)\left(\dfrac{-5+6}{2},\dfrac{2-1}{2}\right)=\left(\dfrac12,\dfrac12\right), and the midpoint of BDBD is (1+02,762)=(12,12)\left(\dfrac{1+0}{2},\dfrac{7-6}{2}\right)=\left(\dfrac12,\dfrac12\right). Naming the vertices consecutively fixes this single configuration.
Q9
Tier 3 · Hard

9

The point P=(x,y)P=(x,y) has a negative yy-coordinate. The points A(4,6)A(-4,6) and B(1,0)B(1,0) are fixed. The midpoint of APAP lies on the yy-axis and PB=5PB=5 units. Find the coordinates of PP. Verify both conditions and explain why the point is unique.

(5)

(Total for Question 9 is 5 marks)

Mark scheme

Mark scheme for question 9
QuestionAnswerMarkMark scheme
9
  • P=(4,4)P=(4,-4)
  • The midpoint of APAP is (0,1)(0,1) and PB=5PB=5
  • The other distance solution is (4,4)(4,4), but its yy-coordinate is positive, so it is rejected
5The midpoint of APAP has xx-coordinate 4+x2\dfrac{-4+x}{2}. Since it lies on the yy-axis, 4+x2=0\dfrac{-4+x}{2}=0, so x=4x=4. Now PB=5PB=5 gives (41)2+(y0)2=5\sqrt{(4-1)^2+(y-0)^2}=5, so 9+y2=259+y^2=25 and y=±4y=\pm4. The stated negative yy-coordinate gives P=(4,4)P=(4,-4). Its midpoint with AA is (0,1)(0,1) and PB=32+(4)2=5PB=\sqrt{3^2+(-4)^2}=5. The only other candidate, (4,4)(4,4), has a positive yy-coordinate, so PP is unique.

Verified exam appearances

SeriesPaperQuestionMarksCalculatorTierLinks
2024-062FQ84AllowedFoundationQPMS
2022-113FQ93AllowedFoundationQPMS
2022-112HQ132AllowedHigherQPMS
2019-111FQ102Non-calculatorFoundationQPMS
2024-111FQ83Non-calculatorFoundationQPMS
2022-111FQ152Non-calculatorFoundationQPMS
2023-061FQ94Non-calculatorFoundationQPMS
2022-062FQ84AllowedFoundationQPMS

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