Finding the Fourth Proportional to 1,385.98, 1,912.79 and 788.65

Step by Step Solution

1. Step 1: Write the proportion equation
   1,385.98 : 1,912.79 = 788.65 : x
2. Step 2: Convert to fraction form
   1,385.98/1,912.79 = 788.65/x
3. Step 3: Cross multiply
   1,385.98x = 1,912.79 × 788.65
4. Step 4: Simplify right side
   1,385.98x = 1,508,519.02
5. Step 5: Solve for x
   x = 1,508,519.02/1,385.98
6. Step 6: Final answer
   x = 1,088.42