This diagram has a heading “Doing.” Underneath, the phrase “number of dollars” is written , followed by an arrow pointing to a box. The box contains the operation “multiply by 0.74.” From the box, a further arrow points to the phrase “number of euros.” Under the first diagram there is a heading “Undoing.” The phrase “number of euros” is followed by an arrow which points to a box. The box contains the operation “divide by 0.74.” From the box a further arrow points to the phrase “number of dollars.”

9.5.3 Changing Formulas