Finding the Fourth Proportional to 1,398.72, 1,930.50 and 839.64

Step by Step Solution

1. Step 1: Write the proportion equation
   1,398.72 : 1,930.50 = 839.64 : x
2. Step 2: Convert to fraction form
   1,398.72/1,930.50 = 839.64/x
3. Step 3: Cross multiply
   1,398.72x = 1,930.50 × 839.64
4. Step 4: Simplify right side
   1,398.72x = 1,620,925.02
5. Step 5: Solve for x
   x = 1,620,925.02/1,398.72
6. Step 6: Final answer
   x = 1,158.86