New
New
Year 10
Higher

The laws of indices - division

I can use the laws of indices to divide two powers where the bases are the same.

New
New
Year 10
Higher

The laws of indices - division

I can use the laws of indices to divide two powers where the bases are the same.

Lesson details

Key learning points

  1. When dividing two terms, you can sometimes write this more simply.
  2. If the powers have the same base, then the powers can be combined into a single power.
  3. The exponent or index of the new power reflects this combination.
  4. By studying the structure of division, you can see how the index will change.
  5. a^b ÷ a^c = a^(b−c)

Common misconception

When dividing terms with coefficients, pupils also subtract the coefficients as well as the exponents.

Pupils should be encouraged to rewrite their expression as a fraction, with the number parts grouped and powers grouped. This hopefully avoids this error as they can see the fraction line as a division.

Keywords

  • Index - An exponent is a number positioned above and to the right of a base value. It indicates repeated multiplication. An alternative word for this is index (plural indices).

  • Coefficient - A numerical coefficient is a constant multiplier of the variables in a term.

  • Power - 16 is the fourth power of 2. Alternatively this can be written as 2^4 which is read as “2 to the power of 4”.

Pupils can make their own word or picture problem similar to question 1 in task B and swap within the class.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

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6 Questions

Q1.
What is the value of $$a$$ for $$a^3 \times a^7 = 12^{10}$$?
Correct Answer: 12
Q2.
What is the value of $$a$$ for $$a^a \times a^a = 9^{18}$$?
Correct Answer: 9
Q3.
What is the value of $$a$$ for $$5^a \times 5^a = 5^{20}$$?
Correct Answer: 10
Q4.
What is the value of $$a$$ for $$8^6 \times 8^{-a} = 8^a$$?
Correct Answer: 3
Q5.
What is the value of $$a$$ for $$10^3 \times 10^a = 10^3$$?
Correct Answer: 0
Q6.
What is the value of $$a$$ for $$9^a = 81$$?
Correct Answer: 1

6 Questions

Q1.
What is the value of $$b$$ for $$b^9 \div b^4 = 6^5$$?
Correct Answer: 6
Q2.
What is the value of $$a$$ for $$9^{20} \div 9^7 = 9^a$$?
Correct Answer: 13
Q3.
What is the value of $$a$$ for $$0.4^8 \div 0.4^a = 0.4$$?
Correct Answer: 7
Q4.
What is the value of $$a$$ for $$\frac{7^a}{7^7} = 7^{12}$$?
Correct Answer: 19
Q5.
What is the value of $$a$$ for $$\frac{5^9}{5^3} = 5^a$$?
Correct Answer: 6
Q6.
What is the value of $$a$$ for $$\frac{x^a}{x^8} = x^{10}$$?
Correct Answer: 18