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Proportional Reasoning-1

Find the value of one

5 notebooks cost ₹90. What do 8 cost?

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Five notebooks cost ₹90.
Step 1 of 3
  1. Five notebooks cost ₹90.
  2. Divide by 5: one notebook is ₹18.
  3. Multiply by 8: eight notebooks are ₹144.

The rule

8 notebooks cost ₹144.

When every item is worth the same, divide to find one item. Multiply to find many. This is the unitary method. To check, divide the answer by the items. You get one item's value.

  • 9 overs bring 54 runs. One over is 54 ÷ 9 = 6 runs.
  • 15 overs, with 6 runs an over, bring 15 × 6 = 90 runs.
  • Check: 90 ÷ 15 = 6 again.

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This track

  1. 0 Start here
  2. 1 How much more, and how many times
  3. 2 What 3 : 2 says, and what it does not
  4. 3 The same comparison in bigger numbers
  5. 4 Match the units, then cut it down
  6. 5 Sharing an amount in a ratio
  7. 6 Checkpoint: comparing, writing and sharing
  8. 7 Two ratios that are equal
  9. 8 Find the value of one
  10. 9 When two amounts grow together
  11. 10 A rate is a ratio with units on it
  12. 11 A scale is a ratio you can walk
  13. 12 Checkpoint: proportion, rates and scales
  14. 13 The big picture
  15. 14 Track quiz

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