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Proportional Reasoning-2

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A pie chart divides a circle into slices. Workers at the same speed finish a job in some days.

Figure 1 — a circle shared out, and pairs that keep one product.

This is Part II, Chapter 3, Proportional Reasoning-2.

What you will learn

  • The whole turn — one circle stands for a whole set. Going round it once is 360°.
  • A slice — a group's own share of the turn.
  • Drawing one — count, share, angle, draw, and check that it closes.
  • Reading one — what a chart can, and cannot, tell you.
  • Two charts — the same picture, two very different totals.
  • One up, one down — two amounts whose product stays fixed. A product is the answer to a multiplication.
  • Which kind — direct, inverse, or neither.
  • At work — workers and days, speed and time.
  • Many terms — a ratio with three or more parts.
  • Sharing a whole — one whole cut into many parts.

Every lesson has a lab. Move the numbers and watch the chart, or the pair, change.

Jump to lesson

This track

  1. 0 Start here
  2. 1 One circle for the whole set
  3. 2 A slice is a share of the turn
  4. 3 Draw a chart, then check it closes
  5. 4 What a chart says, and what it holds back
  6. 5 Two charts that look the same
  7. 6 When one grows and the other shrinks
  8. 7 Which kind is it, or neither
  9. 8 Workers and days, speed and time
  10. 9 A ratio with three parts
  11. 10 Share a whole in many parts
  12. 11 Checkpoint: ratios with many terms
  13. 12 The big picture
  14. 13 Track quiz

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