Finding the Third Proportional to 128.67 and 278.72

Step by Step Solution

1. Step 1: Write the proportion equation
   128.67 : 278.72 = 278.72 : x
2. Step 2: Convert to fraction form
   128.67/278.72 = 278.72/x
3. Step 3: Cross multiply
   128.67x = 278.72 × 278.72
4. Step 4: Simplify right side
   128.67x = 77,684.14
5. Step 5: Solve for x
   x = 77,684.14/128.67
6. Step 6: Final answer
   x = 603.74