Scientific Notation Format
Scientific notation expresses numbers in the form a × 10^n, where the coefficient a satisfies 1 ≤ |a| < 10 and n is a positive or negative integer.
Number = a × 10^n (where 1 ≤ |a| < 10)
Converting To and From Scientific Notation
Converting a standard number to scientific notation:
Step 1: Identify the first significant digit (first non-zero digit).
Step 2: Place the decimal point after this digit to create the coefficient (1 ≤ a < 10).
Step 3: Count how many places the decimal moved — this is the exponent. Moving left = positive exponent. Moving right = negative exponent.
Examples:
45,000,000 → decimal moved 7 places left → 4.5 × 10^7
0.000012 → decimal moved 5 places right → 1.2 × 10^−5
837.5 → decimal moved 2 places left → 8.375 × 10^2
Converting back from scientific notation:
1. Take the coefficient and move the decimal by the exponent places.
2. Positive exponent: move right. Negative exponent: move left.
3. Fill gaps with zeros.
2.56 × 10^4 → move decimal 4 right → 25,600
7.8 × 10^−3 → move decimal 3 left → 0.0078
Arithmetic in Scientific Notation
Performing arithmetic on numbers in scientific notation is efficient once you understand the rules:
Multiplication: Multiply the coefficients and add the exponents.
(3.2 × 10^4) × (2.5 × 10^3) = (3.2 × 2.5) × 10^(4+3) = 8.0 × 10^7
Division: Divide the coefficients and subtract the exponents.
(6.4 × 10^8) ÷ (1.6 × 10^3) = (6.4 ÷ 1.6) × 10^(8−3) = 4.0 × 10^5
Addition/Subtraction: First convert both numbers to the same power of 10, then add or subtract coefficients.
(3.2 × 10^5) + (4.5 × 10^4)
= (3.2 × 10^5) + (0.45 × 10^5)
= 3.65 × 10^5
After multiplying or dividing, adjust if the coefficient is no longer between 1 and 10.
12.5 × 10^6 → 1.25 × 10^7
Scientific Notation in the Real World
Scientific notation is indispensable wherever numbers reach extreme scales:
Astronomy: The distance from Earth to the nearest star (Proxima Centauri) is 4.0 × 10^16 metres. The observable universe is approximately 8.8 × 10^26 metres in diameter. Without scientific notation, these comparisons would be practically impossible.
Chemistry: Avogadro's number — the number of atoms in one mole of substance — is 6.022 × 10^23. The mass of a single hydrogen atom is 1.67 × 10^−27 kg.
Physics: The speed of light is 3 × 10^8 m/s. The charge of an electron is 1.6 × 10^−19 coulombs.
Computing: Storage capacity and processing speed are often expressed in scientific notation. 1 terabyte = 10^12 bytes. Modern CPUs execute billions of operations per second (10^9 per second).
Finance: National debts and GDP figures often reach 10^12 (trillions) or beyond. The US national debt exceeds $3 × 10^13.