Home / 100.80-139.20-69.81

Finding the Fourth Proportional to 100.80, 139.20 and 69.81

Calculator

Solution

The fourth proportional to 100.80, 139.20 and 69.81 is: 96.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    100.80 : 139.20 = 69.81 : x
  2. Step 2: Convert to fraction form
    100.80/139.20 = 69.81/x
  3. Step 3: Cross multiply
    100.80x = 139.20 × 69.81
  4. Step 4: Simplify right side
    100.80x = 9,717.55
  5. Step 5: Solve for x
    x = 9,717.55/100.80
  6. Step 6: Final answer
    x = 96.40

Related Problems

Find fourth proportional to 50.40, 69.60 and 34.91
Half scale
Find fourth proportional to 201.60, 278.40 and 139.62
Double scale
Find fourth proportional to 101.80, 140.58 and 70.81
Similar ratio
Find fourth proportional to 151.20, 208.80 and 104.72
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.