Answer
Find out the what is the total length of the row of half dollars.
To prove
As given
A half dollar coin issued by the united states mint measures 30.61 millimeters across.
Mikk has 9 half dollars.
He lines them up edge in a row.
Than
Total length of the row of the half dollars = 9 × 30.61
= 275.49 millimeters.
Therefore the total length of the row of half dollar is 275.49 millimeters.