Finding the Fourth Proportional to 1,439.59, 1,985.55 and 915.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,439.59 : 1,985.55 = 915.79 : x
2. Step 2: Convert to fraction form
   1,439.59/1,985.55 = 915.79/x
3. Step 3: Cross multiply
   1,439.59x = 1,985.55 × 915.79
4. Step 4: Simplify right side
   1,439.59x = 1,818,346.83
5. Step 5: Solve for x
   x = 1,818,346.83/1,439.59
6. Step 6: Final answer
   x = 1,263.10