The diameter of a penny is 3/4 in. How many pennies are needed to form a row 12in. long?

Also to find the circumference of a circle do you use the radius or diameter x 3.14?

The diameter of a penny is 3/4 in. How many pennies are needed to form a row 12in. long?

12 divided by 3/4

Also to find the circumference of a circle do you use the radius or diameter x 3.14?

The circumference of a circle is

3.142 x diameter

or

2 x 3.142 x radius