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Patterns and Algebra - Grid References and Compass Directions

Grade 6IB

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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The Cartesian coordinate system uses two perpendicular axes: the horizontal xx-axis and the vertical yy-axis.

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A point is located using an ordered pair (x,y)(x, y), where xx is the horizontal distance from the origin and yy is the vertical distance.

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The origin is the point where the two axes intersect, denoted by the coordinates (0,0)(0, 0).

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Compass directions provide a way to describe movement and orientation. The four cardinal directions are North (NN), South (SS), East (EE), and West (WW).

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The four ordinal (intercardinal) directions are Northeast (NENE), Southeast (SESE), Southwest (SWSW), and Northwest (NWNW).

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Movements on a grid can be represented algebraically. Moving East or West affects the xx-coordinate, while moving North or South affects the yy-coordinate.

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A full rotation is 360∘360^\circ. Therefore, a quarter turn (90∘90^\circ) clockwise from North points East, and a half turn (180∘180^\circ) points South.

📐Formulae

Position=(x,y)Position = (x, y)

Translation Rule: (x,y)→(x+a,y+b)\text{Translation Rule: } (x, y) \rightarrow (x + a, y + b)

North=0∘/360∘\text{North} = 0^\circ / 360^\circ

East=90∘\text{East} = 90^\circ

South=180∘\text{South} = 180^\circ

West=270∘\text{West} = 270^\circ

💡Examples

Problem 1:

A treasure chest is located at (3,5)(3, 5) on a map. If a pirate starts at (1,2)(1, 2), how many units East and how many units North must they travel to reach the chest?

Solution:

2 units East, 3 units North2 \text{ units East, } 3 \text{ units North}

Explanation:

To find the distance, subtract the starting coordinates from the target coordinates. For the xx-direction (East): 3−1=23 - 1 = 2. For the yy-direction (North): 5−2=35 - 2 = 3.

Problem 2:

A robot follows the algebraic rule (x,y)→(x+4,y−2)(x, y) \rightarrow (x + 4, y - 2). If the robot starts at position P(2,6)P(2, 6), find its new position P′P'.

Solution:

P′(6,4)P'(6, 4)

Explanation:

Substitute the initial coordinates into the rule: xnew=2+4=6x_{new} = 2 + 4 = 6 and ynew=6−2=4y_{new} = 6 - 2 = 4. The new point is (6,4)(6, 4).

Problem 3:

An explorer is facing North. They turn 225∘225^\circ clockwise. In which direction are they now facing?

Solution:

SW (Southwest)SW \text{ (Southwest)}

Explanation:

A 180∘180^\circ turn clockwise from North faces South. An additional 45∘45^\circ turn (225∘−180∘=45∘225^\circ - 180^\circ = 45^\circ) from South towards the West leads to the Southwest (SWSW) direction.

Problem 4:

Starting at (5,8)(5, 8), a point moves 3 units West and 4 units South. What are the final coordinates?

Solution:

(2,4)(2, 4)

Explanation:

Moving West decreases the xx-coordinate: 5−3=25 - 3 = 2. Moving South decreases the yy-coordinate: 8−4=48 - 4 = 4. The final position is (2,4)(2, 4).