Every formula that recurs on the Science test, in one table. Each is worked through below.
Skill | Formula | What it finds |
|---|
Percent | Part ÷ Whole × 100 | A percentage |
Percent change | Change ÷ Original × 100 | An increase or decrease |
Mean | Sum ÷ Number of values | The average |
Range | Highest − Lowest | The spread |
Density | Mass ÷ Volume | Density |
Speed | Distance ÷ Time | Speed |
Acceleration | Change in velocity ÷ Time | Acceleration |
Force | Mass × Acceleration | Force |
Weight | Mass × Gravity | Weight |
Work | Force × Distance | Work |
Power | Work ÷ Time | Power |
Kinetic energy | ½ × Mass × Velocity² | Energy of motion |
Gravitational potential energy | Mass × Gravity × Height | Stored gravitational energy |
Momentum | Mass × Velocity | Momentum |
Ohm’s law | Voltage = Current × Resistance | Electrical relationships |
Wavelength | Wave speed ÷ Frequency | Wavelength |
Heat transfer | Mass × Specific heat × Temperature change | Thermal energy |
Statistics appear in experiments, tables, population studies and weather records. The official study guide names range, mean, median and mode as the measures you will be asked to calculate from science data.
Measure | How to find it | Example | Result |
|---|
Mean | Sum ÷ number of values | 18, 21, 24, 27, 30 | 120 ÷ 5 = 24 |
Median | Order them, take the middle | 12, 17, 19, 23, 41 | 19 |
Mode | Most frequent value | 14, 17, 17, 21, 26 | 17 |
Range | Highest − lowest | 8, 14, 19, 24, 31 | 31 − 8 = 23 |
With an even number of values, the median is the average of the two middle numbers.
A researcher records bacteria counts in five samples: 84, 91, 91, 103, 151.
The median is 91. The mean is (84 + 91 + 91 + 103 + 151) ÷ 5 = 520 ÷ 5 = 104. The single value of 151 drags the mean about 13 above the median.
When a question asks which measure better represents the center of the data, an obvious outlier points to the median. That one rule answers a lot of Science statistics items.
Percentage = Part ÷ Whole × 100. If 18 of 60 samples show a characteristic, that is 18 ÷ 60 × 100 = 30%.
Percent change = Change ÷ Original × 100. A population rising from 2,400 to 3,600 changes by 1,200, so 1,200 ÷ 2,400 × 100 = 50%.
The common mistake: dividing by the new value instead of the original. Using 3,600 as the denominator gives about 33%, which is wrong but looks reasonable enough to sit in the answer options. The reference is always the value you are measuring change from.
One more distinction the GED tests. A rise of 20 percentage points is not the same as a 20% increase. If a figure moves from 30% to 50%, that is 20 percentage points but a 67% increase, because 20 ÷ 30 is 0.67. Watch which one the question actually asks for.
Temperature items often pair a data table with a conversion. Both directions are worth knowing.
°C = (°F − 32) × 5/9
°F = °C × 9/5 + 32
A table records 18.8°C. Converting to Fahrenheit: 18.8 × 9/5 = 18.8 × 1.8 = 33.84, then 33.84 + 32 = 65.84, so about 65.8°F.
Do the multiplication before the addition. Adding 32 first is the error these items are built around, and it produces 91.4 — a number far enough off to be spotted with a quick sanity check.
Density = Mass ÷ Volume. It describes how much mass sits in a given volume, which is why it identifies a material rather than an amount of it.
A mineral sample with a mass of 540 g and a volume of 200 cm³ has a density of 540 ÷ 200 = 2.7 g/cm³.
The trap: two samples of the same material have the same density regardless of size. A larger sample is not denser. Questions comparing several samples are usually checking whether you know that.
Density also predicts floating. Water is about 1 g/cm³, so anything denser sinks and anything less dense floats. A question giving four materials and asking which floats is really asking you to calculate four densities and compare each against 1.
Speed = Distance ÷ Time. Acceleration = Change in velocity ÷ Change in time.
Units decide the answer as much as the arithmetic. Kilometres with hours gives km/h. Metres with seconds gives m/s. If a problem mixes 2 kilometres with 500 metres, convert first: 2 km = 2,000 m.
Read the units before touching the calculator. A correct formula with mismatched units still produces a wrong answer, and nothing on the screen will warn you.
Acceleration deserves a note of its own. It measures how quickly velocity changes, not how fast something is going. An object moving at a constant 90 km/h has zero acceleration. Questions that describe steady motion and then ask for acceleration are checking exactly that, and the answer is often zero.
Quantity | Formula | Worked example | Result |
|---|
Force | F = m × a | 12 kg object accelerating at 3.5 m/s² | 12 × 3.5 = 42 N |
Weight | W = m × g | 15 kg object, g = 9.8 m/s² | 15 × 9.8 = 147 N |
Work | W = F × d | 80 N moving an object 6 m | 80 × 6 = 480 J |
When a problem supplies a value for gravitational acceleration, use the value given rather than a remembered one — it will not always be 9.8.
Do not confuse work with power. Work measures energy transferred through force over a distance. Power describes how quickly that work is done. Same energy, different time, different power.
Quantity | Formula | Worked example | Result |
|---|
Power | P = Work ÷ Time | 1,200 J of work in 15 seconds | 1,200 ÷ 15 = 80 W |
Kinetic energy | KE = ½mv² | 4 kg object at 10 m/s | ½ × 4 × 100 = 200 J |
Gravitational PE | PE = mgh | 5 kg raised 8 m, g = 9.8 | 5 × 9.8 × 8 = 392 J |
Watch the squared velocity in kinetic energy. Doubling the speed does not double the energy — it quadruples it, because the velocity term is squared before the halving. That relationship is a favorite for conceptual questions that never ask you to calculate anything.
Momentum = Mass × Velocity. A 1,500 kg vehicle traveling at 20 m/s has a momentum of 1,500 × 20 = 30,000 kg·m/s.
Questions often present two objects and ask which has greater momentum. Check both mass and velocity rather than assuming the heavier one wins. A light object moving fast can carry more momentum than a heavy one barely moving.
Momentum is also easy to confuse with kinetic energy, since both combine mass and velocity. Momentum uses velocity once; kinetic energy squares it. Doubling an object’s speed doubles its momentum but quadruples its kinetic energy, which is why the two give different answers to "which object has more".
Ohm’s law: V = IR, where V is voltage, I is current and R is resistance. With a current of 3 A and a resistance of 8 Ω, the voltage is 3 × 8 = 24 V.
Wavelength: λ = v ÷ f, where λ is wavelength, v is wave speed and f is frequency. A wave traveling at 340 m/s with a frequency of 170 Hz has a wavelength of 340 ÷ 170 = 2 m.
Both are rearrangeable, and the GED usually asks for the quantity that is not on the left of the equation as written. Practice solving each one for every variable rather than only in the given direction.
For Ohm’s law that means being equally comfortable with I = V ÷ R and R = V ÷ I. For wavelength it means recognizing that speed and frequency move in opposite directions at a fixed wavelength, so a higher frequency wave at the same speed has a shorter wavelength.
Q = mcΔT, where Q is heat transferred, m is mass, c is specific heat capacity and ΔT is the change in temperature.
For a sample with m = 50 g, c = 4.2 J/g°C and ΔT = 10°C: Q = 50 × 4.2 × 10 = 2,100 J.
The delta symbol means change, not final value. Using the final temperature instead of the difference is the standard error here, and it inflates the answer substantially.
Specific heat capacity is the quantity that varies by material, and it will always be supplied. Water has an unusually high value, which is why questions often use it to illustrate that some substances need far more energy to warm by the same number of degrees.
Scientific notation makes very large and very small measurements manageable. A positive exponent moves the decimal point right; a negative exponent moves it left.
4.2 × 10⁵ = 420,000
4.2 × 10⁻⁵ = 0.000042
Science questions use it for microscopic structures, astronomical distances and large populations. You are rarely asked to convert for its own sake — more often you have to compare two values written this way, where the exponent decides the comparison before the digits do.
A correct formula with the wrong units still produces a wrong answer. Keep this table in view while you practice.
Measurement | Common unit |
|---|
Distance | metre |
Time | second |
Mass | gram or kilogram |
Force | newton (N) |
Energy | joule (J) |
Power | watt (W) |
Current | ampere (A) |
Voltage | volt (V) |
Resistance | ohm (Ω) |
Density | g/cm³ or kg/m³ |
Speed | m/s |
Because the formulas are supplied, the marks sit entirely in application. Ask three questions of every calculation before you start.
What am I trying to find?
Which quantities do I already have?
What units should my answer have?
The third question is the one people skip, and it is the cheapest error check available. If you are solving for speed and your working produces newtons, something went wrong several steps earlier. This is the same reasoning discipline the Assessment Guide for Educators weights most heavily, with quantitative reasoning and data interpretation worth 30% of your score on its own.
Pair this sheet with the GED science cheat sheet for the non-numerical reasoning, then apply both under time pressure in the free GED science practice test. If you also need the math equivalent, the GED math formula sheet covers what Mathematical Reasoning supplies. The official subject pages confirm the current format, timing and calculator policy.
