Write very large or very small numbers as a×10n and calculate with them, keeping the answer in standard form. It is on Foundation and Higher, aimed at grade 5. Free questions with answers are on this page. Worked examples show each line before you try the questions.
Standard form is a×10n with 1≤a<10 and n an integer. Multiply: multiply the as and add the indices. Divide: divide the as and subtract the indices. Then tidy so a is back in range: 32×107=3.2×108. Adding and subtracting need the same power of 10 first.
Calculator: the ×10x key, not 10∧ typed as ordinary digits with a missing bracket. Non-calculator: write the law of indices you used. Answers must be in standard form unless the question asks for an ordinary number.
Multiply/divide the numbers and add/subtract the powers separately, then adjust so the number part is from 1 up to but not including 10. Addition needs the same power of 10 first. Non-calc standard form is a 2-mark staple.
Objectives
Multiply two numbers in standard form.
Divide two numbers in standard form.
Add them when the powers match, and write an integer in standard form.
Key points
Write an ordinary number in standard form and convert back.
Multiply and divide numbers in standard form by dealing with the numbers and the powers separately.
Add and subtract by converting to ordinary numbers or matching the powers of 10.
Adjust an answer like 15×1010 so the front number is between 1 and 10.
Worked examples
Example 1
Work out (3×10^4)×(2×10^3). Give your answer in standard form.
This topic can appear on a calculator or a non-calculator paper. Show enough working for a method mark.
If the question says “show that”, the result is given. The marks are for the steps that reach it.
The method is the same on AQA-style and Edexcel-style papers.
Show the split into 'front numbers' and 'powers' as two separate lines — the method mark is for that.
If the answer is not in standard form yet, write the un-adjusted version first and then the adjusted one, so a slip in adjusting still leaves the method visible.
Printable worksheet
The same questions are in a PDF you can print. Answers start on a later page.