Finding the Fourth Proportional to 1,385.64, 1,909.55 and 991.98

Step by Step Solution

1. Step 1: Write the proportion equation
   1,385.64 : 1,909.55 = 991.98 : x
2. Step 2: Convert to fraction form
   1,385.64/1,909.55 = 991.98/x
3. Step 3: Cross multiply
   1,385.64x = 1,909.55 × 991.98
4. Step 4: Simplify right side
   1,385.64x = 1,894,237.89
5. Step 5: Solve for x
   x = 1,894,237.89/1,385.64
6. Step 6: Final answer
   x = 1,367.05