Finding the Fourth Proportional to 1,012.72, 1,398.72 and 664.96

Step by Step Solution

1. Step 1: Write the proportion equation
   1,012.72 : 1,398.72 = 664.96 : x
2. Step 2: Convert to fraction form
   1,012.72/1,398.72 = 664.96/x
3. Step 3: Cross multiply
   1,012.72x = 1,398.72 × 664.96
4. Step 4: Simplify right side
   1,012.72x = 930,092.85
5. Step 5: Solve for x
   x = 930,092.85/1,012.72
6. Step 6: Final answer
   x = 918.41