Finding the Fourth Proportional to 1,415.78, 1,953.76 and 786.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,415.78 : 1,953.76 = 786.40 : x
2. Step 2: Convert to fraction form
   1,415.78/1,953.76 = 786.40/x
3. Step 3: Cross multiply
   1,415.78x = 1,953.76 × 786.40
4. Step 4: Simplify right side
   1,415.78x = 1,536,436.86
5. Step 5: Solve for x
   x = 1,536,436.86/1,415.78
6. Step 6: Final answer
   x = 1,085.22