Finding the Fourth Proportional to 1,013.96, 1,399.60 and 641.56

Step by Step Solution

1. Step 1: Write the proportion equation
   1,013.96 : 1,399.60 = 641.56 : x
2. Step 2: Convert to fraction form
   1,013.96/1,399.60 = 641.56/x
3. Step 3: Cross multiply
   1,013.96x = 1,399.60 × 641.56
4. Step 4: Simplify right side
   1,013.96x = 897,927.38
5. Step 5: Solve for x
   x = 897,927.38/1,013.96
6. Step 6: Final answer
   x = 885.56