Working with Per Cents

Finding the per cent of a number:
  1. 40% of 50 = .4 x 50 = 20
    40% of 50 = 40/100 x 50 = 2/5 x 50 = 20

  2. 25% of 42 = .25 x 42 = 10.5
    25% of 42 = 25/100 x 42 = 1/4 x 42 = 10 1/2

  3. 5% of 160 = .05 x 160 = 8
    5% of 160 = 5/100 x 160 = 1/20 x 160 = 8

  4. 12 1/2 % of 96 = 12.5% of 96 = .125 x 96 = 12
    12 1/2 % of 96 = 25/2 % of 96 = 25/200 x 96 = 12

  5. 16 2/3 % of 36 = 50/3 % of 36 = 50/300 x 36 = 6 (With repeating decimal, use the fraction approach.)

  6. 1/2 % of 600 = .5% of 600 = 5/1000 x 600 = 3
    1/2 % of 600 = 1/200 x 600 = 3

  7. 50% of 75 = .5 x 75 = 37.5
    50% of 75 = 1/2 x 75 = 37 1/2

  8. 37 1/2 % of $10.50 = .375 x $10.50 = $3.9375 or $3.94
    37 1/2 % of $10.50 = 3/8 x $10.50 = $ 31.50/8 = $3.9375 or $3.94

  9. 150% of 40 = 1.5 x 40 = 60
    150% of 40 = 150/100 x 40 = 3/2 x 40 = 60

Finding the per cent that one number is of another number:

  1. 20 = what per cent of 50?
    20 ÷ 50 x 100% = 2/5 x 100% = 40

  2. 8 = what per cent of 1000?
    8 ÷ 1000 x 100% = 1/125 x 100% = 100/125 % = .8%

  3. 30 = what per cent of 80?
    30 ÷ 80 x 100% = 3 ÷ 8 x 100% = 300/8 % = 37.5%

  4. 50 = what per cent of 75?
    50 ÷ 75 x 100% = 2/3 x 100% = 100/3 % = 66 2/3%

  5. 400 = what per cent of 320?
    400 ÷ 320 x 100% = 5/4 x 100% = 500/4 % = 125%

  6. 3/8 = what per cent of 1/2?
    3/8 ÷ 1/2 x 100% = 3/8 x 2/1 x 100% = 75%