Finding the Fourth Proportional to 28,128.69, 42,065.06 and 21,017.97

Step by Step Solution

1. Step 1: Write the proportion equation
   28,128.69 : 42,065.06 = 21,017.97 : x
2. Step 2: Convert to fraction form
   28,128.69/42,065.06 = 21,017.97/x
3. Step 3: Cross multiply
   28,128.69x = 42,065.06 × 21,017.97
4. Step 4: Simplify right side
   28,128.69x = 884,122,064.04
5. Step 5: Solve for x
   x = 884,122,064.04/28,128.69
6. Step 6: Final answer
   x = 31,431.33