Finding the Fourth Proportional to 1,287.75, 1,931.72 and 518.25

Step by Step Solution

1. Step 1: Write the proportion equation
   1,287.75 : 1,931.72 = 518.25 : x
2. Step 2: Convert to fraction form
   1,287.75/1,931.72 = 518.25/x
3. Step 3: Cross multiply
   1,287.75x = 1,931.72 × 518.25
4. Step 4: Simplify right side
   1,287.75x = 1,001,113.89
5. Step 5: Solve for x
   x = 1,001,113.89/1,287.75
6. Step 6: Final answer
   x = 777.41