Home / 128.87-193.20-56.78

Finding the Fourth Proportional to 128.87, 193.20 and 56.78

Calculator

Solution

The fourth proportional to 128.87, 193.20 and 56.78 is: 85.12

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.87 : 193.20 = 56.78 : x
  2. Step 2: Convert to fraction form
    128.87/193.20 = 56.78/x
  3. Step 3: Cross multiply
    128.87x = 193.20 × 56.78
  4. Step 4: Simplify right side
    128.87x = 10,969.44
  5. Step 5: Solve for x
    x = 10,969.44/128.87
  6. Step 6: Final answer
    x = 85.12

Related Problems

Find fourth proportional to 64.43, 96.60 and 28.39
Half scale
Find fourth proportional to 257.74, 386.39 and 113.56
Double scale
Find fourth proportional to 129.87, 194.70 and 57.78
Similar ratio
Find fourth proportional to 193.30, 289.79 and 85.17
1.5x scale

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.