Finding the Fourth Proportional to 128.32, 176.52 and 100.78

Step by Step Solution

1. Step 1: Write the proportion equation
   128.32 : 176.52 = 100.78 : x
2. Step 2: Convert to fraction form
   128.32/176.52 = 100.78/x
3. Step 3: Cross multiply
   128.32x = 176.52 × 100.78
4. Step 4: Simplify right side
   128.32x = 17,789.69
5. Step 5: Solve for x
   x = 17,789.69/128.32
6. Step 6: Final answer
   x = 138.64