A matchstick's pattern of trapeziums is shown. They are not separate and two neighboring trapeziums have a common matchstick. Can you find the rule for this pattern that gives the number of matchsticks in terms of the number of trapeziums ( where represents the number of trapeziums)?
According to the figure ,(on counting)
1 trapezium requires number of matchsticks
2 trapeziums ( having 1 common matchstick ) require number of matchsticks
3 trapeziums ( having 2 common matchsticks ) require number of matchsticks
Now, if we remove 1 common matchstick from each figure ( and add it separately) , then the remaining make multiples of 4 , i.e , 4,8,12….
So, the required equation can be
(where is the number of trapeziums)