Finding the Third Proportional to 123.78 and 259.49

Step by Step Solution

1. Step 1: Write the proportion equation
   123.78 : 259.49 = 259.49 : x
2. Step 2: Convert to fraction form
   123.78/259.49 = 259.49/x
3. Step 3: Cross multiply
   123.78x = 259.49 × 259.49
4. Step 4: Simplify right side
   123.78x = 67,336.45
5. Step 5: Solve for x
   x = 67,336.45/123.78
6. Step 6: Final answer
   x = 543.98