Finding the Fourth Proportional to 1,213.69, 1,820.72 and 520.36

Step by Step Solution

1. Step 1: Write the proportion equation
   1,213.69 : 1,820.72 = 520.36 : x
2. Step 2: Convert to fraction form
   1,213.69/1,820.72 = 520.36/x
3. Step 3: Cross multiply
   1,213.69x = 1,820.72 × 520.36
4. Step 4: Simplify right side
   1,213.69x = 947,429.86
5. Step 5: Solve for x
   x = 947,429.86/1,213.69
6. Step 6: Final answer
   x = 780.62