Finding the Fourth Proportional to 1,003.12, 1,503.18 and 515.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,003.12 : 1,503.18 = 515.50 : x
2. Step 2: Convert to fraction form
   1,003.12/1,503.18 = 515.50/x
3. Step 3: Cross multiply
   1,003.12x = 1,503.18 × 515.50
4. Step 4: Simplify right side
   1,003.12x = 774,889.29
5. Step 5: Solve for x
   x = 774,889.29/1,003.12
6. Step 6: Final answer
   x = 772.48