Finding the Fourth Proportional to 128.12, 176.81 and 72.10

Step by Step Solution

1. Step 1: Write the proportion equation
   128.12 : 176.81 = 72.10 : x
2. Step 2: Convert to fraction form
   128.12/176.81 = 72.10/x
3. Step 3: Cross multiply
   128.12x = 176.81 × 72.10
4. Step 4: Simplify right side
   128.12x = 12,748.00
5. Step 5: Solve for x
   x = 12,748.00/128.12
6. Step 6: Final answer
   x = 99.50