Finding the Fourth Proportional to 1,402.55, 2,104.12 and 428.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,402.55 : 2,104.12 = 428.72 : x
2. Step 2: Convert to fraction form
   1,402.55/2,104.12 = 428.72/x
3. Step 3: Cross multiply
   1,402.55x = 2,104.12 × 428.72
4. Step 4: Simplify right side
   1,402.55x = 902,078.33
5. Step 5: Solve for x
   x = 902,078.33/1,402.55
6. Step 6: Final answer
   x = 643.17