Which expression is equivalent to 4⁻⁵ × 4⁸?
Unit 2 · Exponents & Scientific Notation
Scientific Notation
A number is in scientific notation when it is a × 10^n with 1 ≤ |a| < 10 and n an integer.
Notes
Moving the decimal
If you move the decimal left, n is positive (large numbers). If you move it right, n is negative (small numbers). When multiplying, multiply the decimals and add the exponents, then restore 1 ≤ |a| < 10.
Vocabulary
scientific notation
A × 10^n where 1 ≤ |A| < 10 and n is an integer.
Example: The mass of Earth is about 5.97 × 10^24 kg.
Worked examples
Try the prompt first. The steps stay folded until you ask to see them.
Multiply
(3.0 × 10^4)(2.5 × 10^(−2))
Common errors
Watch for
Writing 35.0 × 10^3 and calling it scientific notation
The leading factor must be at least 1 and less than 10.
Fix: Rewrite as 3.50 × 10^4.
Explore with an applet
Guided practice
Submit each answer to check it. The key is not shown until you do.
Which expression has a value of 1/16?
Which equation is always true?
Intervention
Place-value chart: each move of the decimal is one power of ten.
Enrichment
Compare 4.2 × 10^7 with 6.1 × 10^6 by converting both to the same power.
Explain your reasoning
Sentence starters · Notice and Wonder · Three Reads · Think-Pair-Share · Compare and Connect · Math Talk · Stronger and Clearer Each Time
- The exponent is negative because the original number is…