A shop sells kaya buns. Every box holds n buns. One morning, 6 boxes come in, and 12 more buns. Then 5 boxes are sold, and 8 of the loose buns. Write how many buns are left, in the simplest form.
Buns left = n + 4
Ans: n + 4
Example 1
Simplify 15 + 7n + 9 − 3n − 4 + 2.
15 + 7n + 9 − 3n − 4 + 2 = 4n + 22
Ans: 4n + 22
How to solve it
Write the morning as it happened, with each term's own sign: 6 n plus 12 minus 5 n minus 8.
Put the same kinds together. The minus in front of 5 n belongs to the 5 n, so it goes with it.
Combine the letters: 6 n minus 5 n leaves n. With just one, write n and not 1 n.
Combine the plain numbers: 12 minus 8 leaves 4.
A letter term and a plain number cannot join, so the simplest form is n plus 4.
Letters with letters. Numbers with numbers. Every minus stays with its own term. And when nothing else can join, you're done.
Practice questions with worked solutions
Question 1 is free to try. The other 5 open in the free trial, each with its full working.
What is the method for simplifying algebraic expressions in P6?
Simplifying means writing an expression in its shortest form without changing what it is worth.
What your child learns here
Simplifying means writing an expression in its shortest form without changing what it is worth. The Primary 6 syllabus asks for simple linear expressions without brackets, so every question here is a row of letter terms and plain numbers joined by plus and minus signs.
Recognise a term: a letter with its number in front, or a plain number, each carrying the sign written just before it.
Group the letter terms together and the plain numbers together, without changing any sign.
Combine the letter terms by adding or subtracting the numbers in front of them, so 7n - 2n is 5n.
Read a letter with no number in front as 1 of that letter, and write the answer n, not 1n.
Stop when no other terms can be combined together: a letter term and a plain number stay apart, as in 5n + 3.
Does the answer make sense?
The simplified expression should have fewer terms than the question, with at most one letter term and one plain number left. Your child can put 1 in place of the letter in both the question and the answer, and the two values must match.
How to practise these questions
The Basic questions train collecting the letter terms and the plain numbers separately, keeping each sign with the term it belongs to. Intermediate questions add longer expressions where letter terms and numbers are scattered, and a lone letter with a minus sign in front of it. If collecting like terms goes astray, go through the written step-by-step solution line by line.
Questions parents ask
What are like terms in algebra? Terms with the same letter, such as 4n and 7n, are like terms and can be combined. Plain numbers are like each other too. A letter term and a plain number are not alike, so 4n + 7 stays as it is.
Does P6 algebra include brackets? The Primary 6 syllabus outcome is simplifying simple linear expressions excluding brackets, so expanding brackets is left for secondary school. Brackets can still appear around an answer that carries a unit, such as (5n + 3) cm.
Why does the minus sign matter so much when simplifying? A minus belongs to the term just after it and decides whether that term is added or taken off. Moving a term without its sign changes the value of the whole expression.
