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Finding the Fourth Proportional to 1,391, 1,919.64 and 770

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Solution

The fourth proportional to 1,391, 1,919.64 and 770 is: 1,062.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,391 : 1,919.64 = 770 : x
  2. Step 2: Convert to fraction form
    1,391/1,919.64 = 770/x
  3. Step 3: Cross multiply
    1,391x = 1,919.64 × 770
  4. Step 4: Simplify right side
    1,391x = 1,478,122.80
  5. Step 5: Solve for x
    x = 1,478,122.80/1,391
  6. Step 6: Final answer
    x = 1,062.63

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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.