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Finding the Fourth Proportional to 691.36, 1,036.80 and 258.40

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Solution

The fourth proportional to 691.36, 1,036.80 and 258.40 is: 387.51

Step by Step Solution

  1. Step 1: Write the proportion equation
    691.36 : 1,036.80 = 258.40 : x
  2. Step 2: Convert to fraction form
    691.36/1,036.80 = 258.40/x
  3. Step 3: Cross multiply
    691.36x = 1,036.80 × 258.40
  4. Step 4: Simplify right side
    691.36x = 267,909.12
  5. Step 5: Solve for x
    x = 267,909.12/691.36
  6. Step 6: Final answer
    x = 387.51

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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.