Finding the Fourth Proportional to 1,378.72, 2,066.72 and 915.35

Step by Step Solution

1. Step 1: Write the proportion equation
   1,378.72 : 2,066.72 = 915.35 : x
2. Step 2: Convert to fraction form
   1,378.72/2,066.72 = 915.35/x
3. Step 3: Cross multiply
   1,378.72x = 2,066.72 × 915.35
4. Step 4: Simplify right side
   1,378.72x = 1,891,768.87
5. Step 5: Solve for x
   x = 1,891,768.87/1,378.72
6. Step 6: Final answer
   x = 1,372.12