Home / 128.79-177.84-90

Finding the Fourth Proportional to 128.79, 177.84 and 90

Calculator

Solution

The fourth proportional to 128.79, 177.84 and 90 is: 124.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    128.79 : 177.84 = 90 : x
  2. Step 2: Convert to fraction form
    128.79/177.84 = 90/x
  3. Step 3: Cross multiply
    128.79x = 177.84 × 90
  4. Step 4: Simplify right side
    128.79x = 16,005.60
  5. Step 5: Solve for x
    x = 16,005.60/128.79
  6. Step 6: Final answer
    x = 124.28

Related Problems

Find fourth proportional to 64.40, 88.92 and 45
Half scale
Find fourth proportional to 257.58, 355.68 and 180
Double scale
Find fourth proportional to 129.79, 179.22 and 91
Similar ratio
Find fourth proportional to 193.19, 266.76 and 135
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.