Finding the Fourth Proportional to 82.90, 123.71 and 82.09

Step by Step Solution

1. Step 1: Write the proportion equation
   82.90 : 123.71 = 82.09 : x
2. Step 2: Convert to fraction form
   82.90/123.71 = 82.09/x
3. Step 3: Cross multiply
   82.90x = 123.71 × 82.09
4. Step 4: Simplify right side
   82.90x = 10,155.35
5. Step 5: Solve for x
   x = 10,155.35/82.90
6. Step 6: Final answer
   x = 122.50