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Expressions using Letter-Numbers

Writing an expression for a real situation

A cinema ticket costs ₹40. A ₹15 booking charge is added once, however many tickets you buy. Let t be the number of tickets.

Each ticket costs ₹40 — that part is 40t.
Step 1 of 3
  1. Each ticket costs ₹40 — that part is 40t.
  2. The booking charge, ₹15, happens once.
  3. Total = 40t + 15.

Rule: find the part charged per one, and the part charged once. Per one means for each ticket. Once means one time in all. The per-one part uses the letter. The once-only amount is added as a plain number.

Check it: 3 tickets cost 40 × 3 + 15 = 120 + 15 = ₹135.

Now an auto fare. The meter starts at ₹30. It adds ₹12 for each km (kilometre). For k km, the fare is 12k + 30. For 5 km, that is 12 × 5 + 30 = ₹90.

Pick a bill. Slide the count. Calculate the total, then use the rule.

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This track

  1. 0 Start here
  2. 1 A letter can hold a number
  3. 2 One rule, written once, for every step
  4. 3 What 3n really means
  5. 4 Putting a number in
  6. 5 Always, or only sometimes
  7. 6 Terms of the same kind
  8. 7 Putting two expressions together
  9. 8 Writing an expression for a real situation
  10. 9 A formula is a rule in letters
  11. 10 Letters in a calendar square
  12. 11 Spot the slip
  13. 12 Checkpoint: formulas, calendars and slips
  14. 13 The big picture
  15. 14 Track quiz

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