Math Background

Percents: When Students Ask

  • Why should I learn this?
    Calculating percents is useful for solving many problems in everyday life. Percents are used to find the interest paid on loans and earned on bank accounts, to compute tips left after a meal, to calculate sales tax, and to compare discounts. An understanding of percent will be very valuable to your students when they become adults and buy expensive items such as automobiles and homes.
  • Why do I multiply by 100 when changing a decimal to a percent?
    When you change a percent to a decimal, you first multiply by 100, but then you affix a percent sign, which means “divide by 100.” Since you are multiplying the decimal by 100 and then dividing it by 100, you are not changing its value at all. You are changing only the way it looks.
  • How can something be more than 100%?
    Many things can't be more than 100%, but some can be. For example, you can't have a shirt made of 125% cotton, since the total of all elements in the shirt must equal 100%. Similarly, you can't eat 130% of the apples, since all the apples together would equal 100%. However, you can increase the amount of something by more than 100%. For example, if a business has profits of $50,000 one year and $75, 000 the next year, the profits for the second year are equal to 150% of the profits from the first year.

Houghton Mifflin Math Grade 6