Finding the Fourth Proportional to 1,387.16, 1,911.72 and 993.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.16 : 1,911.72 = 993.50 : x
2. Step 2: Convert to fraction form
   1,387.16/1,911.72 = 993.50/x
3. Step 3: Cross multiply
   1,387.16x = 1,911.72 × 993.50
4. Step 4: Simplify right side
   1,387.16x = 1,899,293.82
5. Step 5: Solve for x
   x = 1,899,293.82/1,387.16
6. Step 6: Final answer
   x = 1,369.20