Finding the Fourth Proportional to 1,131.79, 1,689.49 and 978.70

Step by Step Solution

1. Step 1: Write the proportion equation
   1,131.79 : 1,689.49 = 978.70 : x
2. Step 2: Convert to fraction form
   1,131.79/1,689.49 = 978.70/x
3. Step 3: Cross multiply
   1,131.79x = 1,689.49 × 978.70
4. Step 4: Simplify right side
   1,131.79x = 1,653,503.86
5. Step 5: Solve for x
   x = 1,653,503.86/1,131.79
6. Step 6: Final answer
   x = 1,460.96