Finding the Fourth Proportional to 1,210.79, 1,670.74 and 686.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,210.79 : 1,670.74 = 686.72 : x
2. Step 2: Convert to fraction form
   1,210.79/1,670.74 = 686.72/x
3. Step 3: Cross multiply
   1,210.79x = 1,670.74 × 686.72
4. Step 4: Simplify right side
   1,210.79x = 1,147,320.50
5. Step 5: Solve for x
   x = 1,147,320.50/1,210.79
6. Step 6: Final answer
   x = 947.58