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Finding the Fourth Proportional to 1,386.80, 1,913.68 and 765.84

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Solution

The fourth proportional to 1,386.80, 1,913.68 and 765.84 is: 1,056.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,386.80 : 1,913.68 = 765.84 : x
  2. Step 2: Convert to fraction form
    1,386.80/1,913.68 = 765.84/x
  3. Step 3: Cross multiply
    1,386.80x = 1,913.68 × 765.84
  4. Step 4: Simplify right side
    1,386.80x = 1,465,572.69
  5. Step 5: Solve for x
    x = 1,465,572.69/1,386.80
  6. Step 6: Final answer
    x = 1,056.80

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.