Calculating quantities from percentages is a common requirement in various fields including chemistry, economics, and statistics. Once you have converted the percentage to a decimal, the next step is to use this decimal to find out how much of a certain quantity is represented by that percentage.
Take, for instance, the textbook exercise where we want to calculate the amount of metal in 375 tons of ore if the metal constitutes 10.5% of the ore. After converting the percentage to a decimal (0.105), multiply this by the total quantity, which gives us the formula: \( \text{{quantity of interest}} = \text{{total quantity}} \times \text{{decimal equivalent of the percentage}} \). Therefore, 375 tons multiplied by 0.105 equals 39.375 tons of metal.
Remember:
- Ensure the total quantity and the percentage are about the same concept or unit before multiplying.
- Double-check your calculations, especially the decimal placement, to avoid significant errors.