Hi there!
Let's start with RATIO AND PROPORTION. First, we'll need to set up a proportion to figure out what 7% of 1.42 is. This is the proportion we'll use: x/1.42 = 7/100. Now, let's cross-multiply: 100x = 9.94. Next, we'll divide to figure out what 7% of 1.42 is: x = 0.0994. Lastly, all we need to do is add that value to 1.42 to figure out the total cost: 1.42 + 0.0994 = $1.5194 in total.
GEOMETRY:
The formula for the circumference of a circle is 2 x pi x radius. Let's plug in the radius to this equation: 2 x pi x 3.1. Now, we need to multiply, first leaving it in terms of pi: 6.2 x pi. The circumference of this circle is 6.2pi or 19.477.
Hope this helps!! :)