Finding the Fourth Proportional to 1,012.45, 1,517.67 and 427.61

Step by Step Solution

1. Step 1: Write the proportion equation
   1,012.45 : 1,517.67 = 427.61 : x
2. Step 2: Convert to fraction form
   1,012.45/1,517.67 = 427.61/x
3. Step 3: Cross multiply
   1,012.45x = 1,517.67 × 427.61
4. Step 4: Simplify right side
   1,012.45x = 648,970.87
5. Step 5: Solve for x
   x = 648,970.87/1,012.45
6. Step 6: Final answer
   x = 640.99