Finding the Fourth Proportional to 1,009.40, 1,510.86 and 521.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,009.40 : 1,510.86 = 521.78 : x
2. Step 2: Convert to fraction form
   1,009.40/1,510.86 = 521.78/x
3. Step 3: Cross multiply
   1,009.40x = 1,510.86 × 521.78
4. Step 4: Simplify right side
   1,009.40x = 788,336.53
5. Step 5: Solve for x
   x = 788,336.53/1,009.40
6. Step 6: Final answer
   x = 781.00