LEARN · EXPLAIN · REVISE

Find the x-coordinate of the centroid.

Read the idea, work independently, then explain what changed.

TOPIC 01

Plane vectors and applications: mixed assessment

A mixed assessment: identify the method, justify it and revise your reasoning.

Use one hint at a time. A correction explains what changed, not just the final answer.

01 / Foundation#Your turn

A=(0,0),\quad B=(21,0),\quad C=(0,3)

Skills and prerequisite lessons

Working and explanation

BUILD THE REASONING

Hint 1

Translate the geometry or physical quantity into vectors and check angle conventions.

Hint 2

Average the three vertex position vectors.

Worked solution

Translate the geometry or physical quantity into vectors and check angle conventions.
Calculate or simplify this relation.
$G=(A+B+C)/3=(7,1)$
The centroid lies two-thirds along each median from the vertex.

The requested value is 7.

Checks and common pitfalls: The centroid lies two-thirds along each median from the vertex.

Think first. Reveal a hint when the class is ready.

Teacher preparation and assessment