Finding the Third Proportional to 535.78 and 780.89

Step by Step Solution

1. Step 1: Write the proportion equation
   535.78 : 780.89 = 780.89 : x
2. Step 2: Convert to fraction form
   535.78/780.89 = 780.89/x
3. Step 3: Cross multiply
   535.78x = 780.89 × 780.89
4. Step 4: Simplify right side
   535.78x = 609,790.17
5. Step 5: Solve for x
   x = 609,790.17/535.78
6. Step 6: Final answer
   x = 1,138.13