Finding the Fourth Proportional to 1,012.93, 1,397.15 and 639.59

Step by Step Solution

1. Step 1: Write the proportion equation
   1,012.93 : 1,397.15 = 639.59 : x
2. Step 2: Convert to fraction form
   1,012.93/1,397.15 = 639.59/x
3. Step 3: Cross multiply
   1,012.93x = 1,397.15 × 639.59
4. Step 4: Simplify right side
   1,012.93x = 893,603.17
5. Step 5: Solve for x
   x = 893,603.17/1,012.93
6. Step 6: Final answer
   x = 882.20