Finding the Fourth Proportional to 1,036.21, 1,429.43 and 642.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,036.21 : 1,429.43 = 642.55 : x
2. Step 2: Convert to fraction form
   1,036.21/1,429.43 = 642.55/x
3. Step 3: Cross multiply
   1,036.21x = 1,429.43 × 642.55
4. Step 4: Simplify right side
   1,036.21x = 918,472.37
5. Step 5: Solve for x
   x = 918,472.37/1,036.21
6. Step 6: Final answer
   x = 886.38