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Finding the Fourth Proportional to 987.80, 1,359.60 and 931.10

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Solution

The fourth proportional to 987.80, 1,359.60 and 931.10 is: 1,281.56

Step by Step Solution

  1. Step 1: Write the proportion equation
    987.80 : 1,359.60 = 931.10 : x
  2. Step 2: Convert to fraction form
    987.80/1,359.60 = 931.10/x
  3. Step 3: Cross multiply
    987.80x = 1,359.60 × 931.10
  4. Step 4: Simplify right side
    987.80x = 1,265,923.56
  5. Step 5: Solve for x
    x = 1,265,923.56/987.80
  6. Step 6: Final answer
    x = 1,281.56

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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.