3 pens cost $2.70. What is the cost per pen?

Rectangle divided into 3 units. First unit blank with a note underneath: cost per pen. Second unit has entry: $2.70. Third unit is blank.

$per pen

$0.90 per pen

2.70/3=.90

the mistake in the pattern is that :

b. the decimal point was moved one too many place values each time

the correct pattern could be made by :

b. moving the decimal point to the right the same numbers of place values as the exponents