Finding the Fourth Proportional to 1,403.12, 2,104.72 and 429.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,403.12 : 2,104.72 = 429.20 : x
2. Step 2: Convert to fraction form
   1,403.12/2,104.72 = 429.20/x
3. Step 3: Cross multiply
   1,403.12x = 2,104.72 × 429.20
4. Step 4: Simplify right side
   1,403.12x = 903,345.82
5. Step 5: Solve for x
   x = 903,345.82/1,403.12
6. Step 6: Final answer
   x = 643.81