Finding the Fourth Proportional to 1,438.19, 1,984.10 and 878.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,438.19 : 1,984.10 = 878.21 : x
2. Step 2: Convert to fraction form
   1,438.19/1,984.10 = 878.21/x
3. Step 3: Cross multiply
   1,438.19x = 1,984.10 × 878.21
4. Step 4: Simplify right side
   1,438.19x = 1,742,442.15
5. Step 5: Solve for x
   x = 1,742,442.15/1,438.19
6. Step 6: Final answer
   x = 1,211.56