Finding the Fourth Proportional to 1,223.86, 1,688.51 and 782.01

Step by Step Solution

1. Step 1: Write the proportion equation
   1,223.86 : 1,688.51 = 782.01 : x
2. Step 2: Convert to fraction form
   1,223.86/1,688.51 = 782.01/x
3. Step 3: Cross multiply
   1,223.86x = 1,688.51 × 782.01
4. Step 4: Simplify right side
   1,223.86x = 1,320,431.71
5. Step 5: Solve for x
   x = 1,320,431.71/1,223.86
6. Step 6: Final answer
   x = 1,078.91