💡 Three Skills in One Passage
This GED passage uses one data table to test three different math skills: percent change (how much did price increase?), probability (what fraction of months showed an increase?), and scatter plots (which graph correctly shows inventory vs. price?). This lesson teaches all three!
Inventory (months): Predicted number of months to sell that month's supply of houses
Median Sales Price: The middle value of all house prices sold that month (half sold above, half below)
| Month | Inventory (months) | Median Sales Price | Price vs. Prev. Month |
|---|---|---|---|
| January | 6.3 | $221,700 | — (first month) |
| February | 4.9 | $239,900 | ▲ +$18,200 |
| March | 4.3 | $239,800 | ▼ −$100 |
| April | 4.2 | $236,400 | ▼ −$3,400 |
| May | 4.2 | $239,200 | ▲ +$2,800 |
| June | 4.2 | $232,600 | ▼ −$6,600 |
| July | 4.3 | $237,400 | ▲ +$4,800 |
| August | 4.7 | $253,200 | ▲ +$15,800 |
July → August: Largest single-month price jump (+$15,800) — this is what Q1 tests
Price increases (excluding Jan): Feb, May, July, August = 4 out of 7 months — this is what Q2 tests
Lower inventory → higher price? This relationship is what the scatter plot (Q3) tests
1. Find the change (New − Old)
2. Divide the change by the original (Old) value
3. Multiply by 100 to convert to a percent
New − Old = $253,200 − $237,400 = $15,800
$15,800 ÷ $237,400 = 0.06655...
0.06655 × 100 = 6.655% ≈ 6.7%
| Choice | How You'd Get It | Correct? |
|---|---|---|
| 6.7% | $15,800 ÷ $237,400 × 100 = 6.655% ≈ 6.7% ✅ | ✅ CORRECT |
| 15.8% | Divided change by August price (wrong denominator!) ❌ | ❌ Trap! |
| 6.2% | Close but rounding error ❌ | ❌ Wrong |
| 14.2% | Used wrong months or values ❌ | ❌ Wrong |
Always divide by the ORIGINAL (Old) value — NOT the new value.
15.8% comes from $15,800 ÷ $253,200 × 100 — that's the new (August) price. Always use July (the starting month)!
Feb: $239,900 > $221,700 ✅
Mar: $239,800 < $239,900 ❌
Apr: $236,400 < $239,800 ❌
May: $239,200 > $236,400 ✅
Jun: $232,600 < $239,200 ❌
Jul: $237,400 > $232,600 ✅
Aug: $253,200 > $237,400 ✅
→ 4 months increased
P = favorable ÷ total = 4 ÷ 7 = 4/7
| Month | Price vs. Prev. | Increase? |
|---|---|---|
| February | $239,900 vs $221,700 | ✅ Yes (+$18,200) |
| March | $239,800 vs $239,900 | ❌ No (−$100) |
| April | $236,400 vs $239,800 | ❌ No (−$3,400) |
| May | $239,200 vs $236,400 | ✅ Yes (+$2,800) |
| June | $232,600 vs $239,200 | ❌ No (−$6,600) |
| July | $237,400 vs $232,600 | ✅ Yes (+$4,800) |
| August | $253,200 vs $237,400 | ✅ Yes (+$15,800) |
| Total increases / Total months | 4 / 7 = 4/7 | |
When a problem says "X affects Y" or "does X determine Y?", the convention is:
X-axis (horizontal): The variable that might be the cause (inventory)
Y-axis (vertical): The variable that might be the effect (median sales price)
Median Sales Price is the dependent variable (y-axis)
Y-axis labeled "Median Sales Price (thousands)" with values 220 to 260
Looking at the data: when inventory is LOW (4.2–4.3 months) prices tend to be HIGHER ($236K–$239K). When inventory is HIGH (6.3 months = January), price is lowest ($221K). This suggests a negative relationship — as inventory increases, price tends to decrease.
Before trying to answer questions, read every column title carefully. "Inventory (months)" means "months needed to sell" — not number of houses!
New − Old = change. Change ÷ Old × 100 = %. Never divide by the New (larger) value — that's the #1 error.
List all possible outcomes. Count favorable ones. Watch for "excluding January" type conditions — they change your total!
"Does X affect Y?" → X goes on the horizontal axis, Y goes on the vertical axis. Check axis labels and scales match the data range.
Median is the MIDDLE value. It's not the average. On the GED, "median sales price" means exactly half of homes sold above and half below that price.
| Skill | Formula | This Passage |
|---|---|---|
| Percent Change | (New−Old)÷Old×100 | 6.7% |
| Probability | Favorable÷Total | 4/7 |
| Scatter Plot | Cause=X, Effect=Y | Inventory=X |
| Month | Inventory | Median Price |
|---|---|---|
| January | 6.3 | $221,700 |
| February | 4.9 | $239,900 |
| March | 4.3 | $239,800 |
| April | 4.2 | $236,400 |
| May | 4.2 | $239,200 |
| June | 4.2 | $232,600 |
| July | 4.3 | $237,400 |
| August | 4.7 | $253,200 |