Percentage decrease

If we are asked to decrease a quantity by a certain percentage, we can follow these steps:

• Find the decimal multiplier of the percentage decrease.
• Multiply the original quantity by the decimal multiplier.

Finding the decimal multiplier

The decimal multiplier for a percentage decrease can be found using the formula:

\text{decimal multiplier} = (\frac{\text{percentage decrease}}{100} - 1)

In other words, we convert the percentage decrease to a decimal, and then subtract that decimal from 1.

Finding the percentage decrease

Once we’ve found the decimal multiplier, simply multiply the original quantity by the decimal multiplier to find the decreased amount.

Example: decrease $50 by 20%

1. Find the decimal multiplier:

• \text{decimal multiplier} = (\frac{20}{100} - 1) = 0.2 - 1 = 0.8

2. Multiply the original quantity by the decimal multiplier:

• 50 \times 0.8 = 40

Answer: 40

Example: decrease 120kg by 15%

1. Find the decimal multiplier:

• \text{decimal multiplier} = (\frac{15}{100} - 1) = 0.15 - 1 = 0.85

2. Multiply the original quantity by the decimal multiplier:

• 120 \times 0.85 = 102

Answer: 102kg

Example: decrease 250 by 5%

1. Find the decimal multiplier:

• \text{decimal multiplier} = (\frac{5}{100} - 1) = 0.05 - 1 = 0.95

2. Multiply the original quantity by the decimal multiplier:

• 250 \times 0.95 = 237.5

Answer: 237.5

Example: decrease $80 by 12.5%

1. Find the decimal multiplier:

• \text{decimal multiplier} = (\frac{12.5}{100} - 1) = 0.125 - 1 = 0.875

2. Multiply the original quantity by the decimal multiplier:

• 80 \times 0.875 = 70

Answer: 70

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