Decimal Multipliers — Multiply & Divide Pathway

Using decimal multipliers

  • A multiplier is a decimal that represents a percentage change.
  • Increase by 20%: multiplier = 1.20.
  • Decrease by 15%: multiplier = 0.85.
  • Multiply the original amount by the multiplier to get the new value.

Example: Increase 80 by 10%

  1. Step 1: Multiplier = 1 + 0.10 = 1.10.
  2. Step 2: 80 x 1.10.
  3. Step 3: 80 x 1 = 80. 80 x 0.10 = 8.
  4. Step 4: 80 + 8 = 88. Answer: 88.

Your turn

  • Try: Decrease 60 by 25%.
  • Multiplier = 1 - 0.25 = 0.75.
  • 60 x 0.75.
  • 60 x 0.75 = 45. Answer: 45.

Common Mistakes to Avoid

  • Using the wrong multiplier. Increase means add to 1 (e.g. 20% increase = 1.20). Decrease means subtract from 1 (e.g. 15% decrease = 0.85).
  • Forgetting that 100% is 1.00. No change at all would use a multiplier of 1.00.

Real-Life Example

A jacket costs 80 pounds and increases by 10%. Multiplier = 1.10. 80 x 1.10 = 88 pounds. The new price is 88 pounds.

Extra Support Hints

  • Write the multiplier clearly: increase = 1 + decimal, decrease = 1 - decimal.
  • Check: an increase should give a bigger number, a decrease a smaller one.
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