Finding the Fourth Proportional to 82.18, 123.28 and 21.31

Step by Step Solution

1. Step 1: Write the proportion equation
   82.18 : 123.28 = 21.31 : x
2. Step 2: Convert to fraction form
   82.18/123.28 = 21.31/x
3. Step 3: Cross multiply
   82.18x = 123.28 × 21.31
4. Step 4: Simplify right side
   82.18x = 2,627.10
5. Step 5: Solve for x
   x = 2,627.10/82.18
6. Step 6: Final answer
   x = 31.97