Step-by-step explanation:
arithmetic sequence.
an = an-1 + c = a1 + (n-1)c
c is in our case 2 (every new shape has 2 more vertices).
we have a a1 = 3.
an = 3 + 2(n-1)
so,
a21 = 3 + 2(20) = 3 + 40 = 43
the 21st shadow will have 43 vertices.
They both measure/display the outside distance of a figure
The sum for those numbers is 19.179 NOT 18.729. HOWEVER the Estimation of the sum and the answer for this question is 19.2 because the decimal place you are finding has a number to its right that is greater to that decimal place so you add the one to the decimal place you are finding.
