Finding the Fourth Proportional to 1,920.15, 2,648.82 and 1,290.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,920.15 : 2,648.82 = 1,290.81 : x
2. Step 2: Convert to fraction form
   1,920.15/2,648.82 = 1,290.81/x
3. Step 3: Cross multiply
   1,920.15x = 2,648.82 × 1,290.81
4. Step 4: Simplify right side
   1,920.15x = 3,419,123.34
5. Step 5: Solve for x
   x = 3,419,123.34/1,920.15
6. Step 6: Final answer
   x = 1,780.65