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Finding the Fourth Proportional to 1,210.80, 1,670.80 and 687

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Solution

The fourth proportional to 1,210.80, 1,670.80 and 687 is: 948.00

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,210.80 : 1,670.80 = 687 : x
  2. Step 2: Convert to fraction form
    1,210.80/1,670.80 = 687/x
  3. Step 3: Cross multiply
    1,210.80x = 1,670.80 × 687
  4. Step 4: Simplify right side
    1,210.80x = 1,147,839.60
  5. Step 5: Solve for x
    x = 1,147,839.60/1,210.80
  6. Step 6: Final answer
    x = 948.00

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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.