Finding the Fourth Proportional to 1,421.30, 1,985.50 and 1,421.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,421.30 : 1,985.50 = 1,421.30 : x
2. Step 2: Convert to fraction form
   1,421.30/1,985.50 = 1,421.30/x
3. Step 3: Cross multiply
   1,421.30x = 1,985.50 × 1,421.30
4. Step 4: Simplify right side
   1,421.30x = 2,821,991.15
5. Step 5: Solve for x
   x = 2,821,991.15/1,421.30
6. Step 6: Final answer
   x = 1,985.50