Finding the Fourth Proportional to 1,384.86, 1,909.26 and 991.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,384.86 : 1,909.26 = 991.20 : x
2. Step 2: Convert to fraction form
   1,384.86/1,909.26 = 991.20/x
3. Step 3: Cross multiply
   1,384.86x = 1,909.26 × 991.20
4. Step 4: Simplify right side
   1,384.86x = 1,892,458.51
5. Step 5: Solve for x
   x = 1,892,458.51/1,384.86
6. Step 6: Final answer
   x = 1,366.53