Finding the Fourth Proportional to 1,036.05, 1,428.42 and 642.39

Step by Step Solution

1. Step 1: Write the proportion equation
   1,036.05 : 1,428.42 = 642.39 : x
2. Step 2: Convert to fraction form
   1,036.05/1,428.42 = 642.39/x
3. Step 3: Cross multiply
   1,036.05x = 1,428.42 × 642.39
4. Step 4: Simplify right side
   1,036.05x = 917,602.72
5. Step 5: Solve for x
   x = 917,602.72/1,036.05
6. Step 6: Final answer
   x = 885.67