Finding the Fourth Proportional to 2,145.47, 3,218.15 and 991.22

Step by Step Solution

1. Step 1: Write the proportion equation
   2,145.47 : 3,218.15 = 991.22 : x
2. Step 2: Convert to fraction form
   2,145.47/3,218.15 = 991.22/x
3. Step 3: Cross multiply
   2,145.47x = 3,218.15 × 991.22
4. Step 4: Simplify right side
   2,145.47x = 3,189,894.64
5. Step 5: Solve for x
   x = 3,189,894.64/2,145.47
6. Step 6: Final answer
   x = 1,486.80