if a / b = c / d, then d ⋅ a = b ⋅ c

Start from the conclusion and work back up the proof. Click the arrow to show the parents.

• d ⋅ a = b ⋅ c,

  if the following are true:

  • a = b
  • a = c
  • b = d

  then c = d

  • (b ⋅ d) ⋅ (a / b) = (b ⋅ d) ⋅ (c / d),

    if a = b, then c ⋅ a = c ⋅ b

    • a / b = c / d
  • (b ⋅ d) ⋅ (a / b) = d ⋅ a, (b ⋅ d) ⋅ (a / b) = d ⋅ a
  • (b ⋅ d) ⋅ (c / d) = b ⋅ c, (b ⋅ d) ⋅ (c / d) = b ⋅ c