Home / 65.99-91.07-39.78

Finding the Fourth Proportional to 65.99, 91.07 and 39.78

Calculator

Solution

The fourth proportional to 65.99, 91.07 and 39.78 is: 54.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    65.99 : 91.07 = 39.78 : x
  2. Step 2: Convert to fraction form
    65.99/91.07 = 39.78/x
  3. Step 3: Cross multiply
    65.99x = 91.07 × 39.78
  4. Step 4: Simplify right side
    65.99x = 3,622.57
  5. Step 5: Solve for x
    x = 3,622.57/65.99
  6. Step 6: Final answer
    x = 54.90

Related Problems

Find fourth proportional to 33.00, 45.53 and 19.89
Half scale
Find fourth proportional to 131.98, 182.13 and 79.56
Double scale
Find fourth proportional to 66.99, 92.44 and 40.78
Similar ratio
Find fourth proportional to 98.99, 136.60 and 59.67
1.5x scale

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.