Draw and use a double number line diagram to model and solve the problem below.
Alex wants to make a fleece blanket to cheer up her friend. One yard of material cost $3.90. If Alex wants to purchase 3.5 yards of fleece to make the blanket, what is the total cost?
Here is the double number line diagram:
```
0 1 2 3 4
|---------|---------|---------|---------|
$0 $1.95 $3.90 $5.85 $7.80
|---------|---------|---------|---------|
1 2 3 4
```
The diagram shows the cost of the material on the top line and the number of yards on the bottom line. The tick marks on the bottom line represent half-yards.
To find the cost of 3.5 yards of material, we can start at 3 yards on the bottom line and move halfway to 4 yards. Then we can move up to the top line to find the corresponding cost. The total cost is $13.65.
Therefore, the total cost of 3.5 yards of fleece is $13.65.