Finding the Fourth Proportional to 3,987.28, 5,978.76 and 1,213.12

Step by Step Solution

1. Step 1: Write the proportion equation
   3,987.28 : 5,978.76 = 1,213.12 : x
2. Step 2: Convert to fraction form
   3,987.28/5,978.76 = 1,213.12/x
3. Step 3: Cross multiply
   3,987.28x = 5,978.76 × 1,213.12
4. Step 4: Simplify right side
   3,987.28x = 7,252,953.33
5. Step 5: Solve for x
   x = 7,252,953.33/3,987.28
6. Step 6: Final answer
   x = 1,819.02