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Finding the Fourth Proportional to 718.80, 1,078.20 and 661.20

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Solution

The fourth proportional to 718.80, 1,078.20 and 661.20 is: 991.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    718.80 : 1,078.20 = 661.20 : x
  2. Step 2: Convert to fraction form
    718.80/1,078.20 = 661.20/x
  3. Step 3: Cross multiply
    718.80x = 1,078.20 × 661.20
  4. Step 4: Simplify right side
    718.80x = 712,905.84
  5. Step 5: Solve for x
    x = 712,905.84/718.80
  6. Step 6: Final answer
    x = 991.80

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.