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Decimal values · Cubic Championship

When x is a number like 2.5

Everything works the same as before. The only difference is that the numbers at each step are decimals. Take it slowly and you will be fine.

Same steps, trickier numbers

When your car shows x = 2.5, you do exactly the same thing as always. Swap x for 2.5. Work out each part. Add them together.

The rules have not changed. The arithmetic is just a bit harder.

3x + 4, with x = 2.5

3x + 4 = 11.5
Your car: x = 2.5
  1. Swap x for 2.5
    3 × 2.5 + 4
  2. Multiply first — 3 × 2.5 = 7.5
    7.5 + 4
  3. Add
    11.5 ✓

2x² + 1, with x = 2.5

2x² + 1 = 13.5
Your car: x = 2.5
  1. Swap x for 2.5
    2 × (2.5)² + 1
  2. Square first — (2.5) × (2.5) = 6.25
    2 × 6.25 + 1
  3. Multiply — 2 × 6.25 = 12.5
    12.5 + 1
  4. Add
    13.5 ✓

Key point

2.5 × 2.5 = 6.25. Not 5. Not 4.5. Take your time with this step.

x³ + 2x² + 3x + 4, with x = 2.5

Do it one part at a time.

  1. Part 1 — (2.5) × (2.5) × (2.5)
    2.5 × 2.5 = 6.25  →  6.25 × 2.5 = 15.625
    Part 1 = 15.625
  2. Part 2 — 2 × (2.5)² = 2 × 6.25 = 12.5
    Part 2 = 12.5
  3. Part 3 — 3 × 2.5 = 7.5
    Part 3 = 7.5
  4. Part 4 — just the number
    Part 4 = 4
  5. Add them up
    15.625 + 12.5 + 7.5 + 4 = 39.625

The game rounds to two decimal places

The battery will not show 39.625. It will show 39.63.

The game always rounds to two decimal places.

How rounding works: look at the third decimal place.

  • 39.625 third decimal is 5 — round up the second → 39.63
  • 15.624 third decimal is 4 — leave the second as it is → 15.62
  • 7.500 no third decimal needed — remove the zero → 7.5
  • 14.00 remove both zeros → 14

When you work out the answer, round it to two decimal places before checking it against the battery.

Negative decimals work the same way

If x = −1.5:

  1. (−1.5) × (−1.5)
    = 2.25
    Positive ✓

Squaring removes the negative.

  1. (−1.5) × (−1.5) × (−1.5)
    = 2.25 × (−1.5) = −3.375
    Negative ✓

Cubing keeps the negative.

Same rules as before. Just with decimals.

Three easy mistakes

Mistake 1

Getting 2.5 × 2.5 wrong

Some people write 2.5 × 2.5 = 5. That is 2.5 + 2.5. Multiplication and addition are not the same thing.

2.5 × 2.5 = 6.25.

Mistake 2

Not rounding before checking the battery

You work out 39.625 but look for a battery showing 39.625. The battery shows 39.63.

Always round to two decimal places before you check.

Mistake 3

Forgetting the sign rules with negative decimals

(−1.5)² is positive. (−1.5)³ is negative. ² removes the negative. ³ keeps it.

Same as with whole numbers.

Try one yourself

Your car:

Round your answer to two decimal places

    That is everything in the game

    If you have read through all the maths help pages, you have covered every type of battery in Volt Racers. Go back and race. See if it feels different now.

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    Four-part batteries

    Go back to review four-part batteries without decimals first.
    ← Four-part batteries
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