Finding the Fourth Proportional to 86.24, 128.74 and 83.00

Step by Step Solution

1. Step 1: Write the proportion equation
   86.24 : 128.74 = 83.00 : x
2. Step 2: Convert to fraction form
   86.24/128.74 = 83.00/x
3. Step 3: Cross multiply
   86.24x = 128.74 × 83.00
4. Step 4: Simplify right side
   86.24x = 10,684.88
5. Step 5: Solve for x
   x = 10,684.88/86.24
6. Step 6: Final answer
   x = 123.90