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Finding the Fourth Proportional to 1,987.20, 2,978.28 and 891.52

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Solution

The fourth proportional to 1,987.20, 2,978.28 and 891.52 is: 1,336.15

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,987.20 : 2,978.28 = 891.52 : x
  2. Step 2: Convert to fraction form
    1,987.20/2,978.28 = 891.52/x
  3. Step 3: Cross multiply
    1,987.20x = 2,978.28 × 891.52
  4. Step 4: Simplify right side
    1,987.20x = 2,655,196.19
  5. Step 5: Solve for x
    x = 2,655,196.19/1,987.20
  6. Step 6: Final answer
    x = 1,336.15

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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.