2. Maths for Pysch

• 1. Percentages

  Show number as percentage of another:

  • divide 1st number by 2nd (becomes fraction, so switch it to decimal).
  • multiply answer by 100.

  E.g. show 23 out of 50 as %.

  • 23 ÷ 50 = 23/50 or 0.46
  • 0.46 x 100 = 46%.
• 1a. Percentages

  Find percentage of number:

  • divide % by 100 to get decimal.
  • multiply number by decimal.

  E.g. Find 7% of 340.

  • 7 ÷ 100 = 0.07
  • 340 x 0.07 = 23.8
• 1b. Percentages


  Show 6 out of 10 as percentage.

  • 6 ÷ 10 = 0.6.
  • 0.6 x 100 = 60%
• 1c. Percentages


  Find 60% of 10.

  • 60 ÷ 100 = 0.6
  • 0.6 x 10 = 6
• 1d. Percentages 


  Percentage Change - Formula:

  • % change = change ÷ original x 100.

  E.g. percentage decrease from 16 to 10:

  • 16 - 10 = 6 ÷ 16 = 0.375.
  • 0.375 x 100 = 37.5%.
• 2. Ratios


  Compares quantities.

  • 🐣 🐣 🐣 🐸 🐸 🐸 🐸 🐸
  • ratio of 🐣 to 🐸 is 3:5.