Matchstick patterns
This task is about patterns and rules.
Christine began making the pentagon pattern below with matches.
She noticed a relationship between the number of pentagons and the total number of matches used, which she recorded on a chart.


a) 
Complete the chart above to show the number of matches used.


b) 
How many matches would be needed for 30 pentagons? __________ matches


c) 
Complete the rule below which you could use to find the number of matches needed for any number of pentagons.
Rule: "The number of pentagons × ___________ + ___________ = the number of matches." 