Finding the Fourth Proportional to 1,108.46, 1,529.98 and 642.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,108.46 : 1,529.98 = 642.80 : x
2. Step 2: Convert to fraction form
   1,108.46/1,529.98 = 642.80/x
3. Step 3: Cross multiply
   1,108.46x = 1,529.98 × 642.80
4. Step 4: Simplify right side
   1,108.46x = 983,461.89
5. Step 5: Solve for x
   x = 983,461.89/1,108.46
6. Step 6: Final answer
   x = 887.24