Finding the Fourth Proportional to 1,428.90, 1,971.59 and 869.69

Step by Step Solution

1. Step 1: Write the proportion equation
   1,428.90 : 1,971.59 = 869.69 : x
2. Step 2: Convert to fraction form
   1,428.90/1,971.59 = 869.69/x
3. Step 3: Cross multiply
   1,428.90x = 1,971.59 × 869.69
4. Step 4: Simplify right side
   1,428.90x = 1,714,657.90
5. Step 5: Solve for x
   x = 1,714,657.90/1,428.90
6. Step 6: Final answer
   x = 1,199.98