Finding the Fourth Proportional to 1,003.90, 1,504.79 and 345.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,003.90 : 1,504.79 = 345.57 : x
2. Step 2: Convert to fraction form
   1,003.90/1,504.79 = 345.57/x
3. Step 3: Cross multiply
   1,003.90x = 1,504.79 × 345.57
4. Step 4: Simplify right side
   1,003.90x = 520,010.28
5. Step 5: Solve for x
   x = 520,010.28/1,003.90
6. Step 6: Final answer
   x = 517.99