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Finding the Fourth Proportional to 978.08, 1,348.80 and 646.40

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Solution

The fourth proportional to 978.08, 1,348.80 and 646.40 is: 891.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    978.08 : 1,348.80 = 646.40 : x
  2. Step 2: Convert to fraction form
    978.08/1,348.80 = 646.40/x
  3. Step 3: Cross multiply
    978.08x = 1,348.80 × 646.40
  4. Step 4: Simplify right side
    978.08x = 871,864.32
  5. Step 5: Solve for x
    x = 871,864.32/978.08
  6. Step 6: Final answer
    x = 891.40

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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.