Finding the Fourth Proportional to 1,345.76, 1,856.16 and 991.80

Step by Step Solution

1. Step 1: Write the proportion equation
   1,345.76 : 1,856.16 = 991.80 : x
2. Step 2: Convert to fraction form
   1,345.76/1,856.16 = 991.80/x
3. Step 3: Cross multiply
   1,345.76x = 1,856.16 × 991.80
4. Step 4: Simplify right side
   1,345.76x = 1,840,939.49
5. Step 5: Solve for x
   x = 1,840,939.49/1,345.76
6. Step 6: Final answer
   x = 1,367.96