Put 4,000,000 in scientific notation.

• A. 4x10^6
• B. 4x10^7
• C. 0.4x10^7
• D. 40x10^5

Answer: (A)

Expressing a number in scientific notation means writing it as a × 10^n where the coefficient a is between 1 and 10. For 4,000,000, move the decimal so only one nonzero digit stays to the left: 4.000000 × 10^6, which simplifies to 4 × 10^6. The exponent is 6 because the decimal moved six places to the left (there are six zeros after the 4).

Other representations would give the same value but don’t follow the standard form. For example, 4 × 10^7 equals 40,000,000, which is too large for this number. 0.4 × 10^7 equals 4,000,000 as well, but the coefficient is less than 1, not the conventional form. And 40 × 10^5 also equals 4,000,000 but isn’t written in the standard single-digit coefficient form. So the best, conventional representation is 4 × 10^6.