Finding the Fourth Proportional to 2,631.38, 3,948.47 and 987.78

Step by Step Solution

1. Step 1: Write the proportion equation
   2,631.38 : 3,948.47 = 987.78 : x
2. Step 2: Convert to fraction form
   2,631.38/3,948.47 = 987.78/x
3. Step 3: Cross multiply
   2,631.38x = 3,948.47 × 987.78
4. Step 4: Simplify right side
   2,631.38x = 3,900,214.76
5. Step 5: Solve for x
   x = 3,900,214.76/2,631.38
6. Step 6: Final answer
   x = 1,482.20