3
Describing and sorting expressions in words
Discover Mathematics P6: Term 1, Unit 3, Lessons 1–2
GoalRead an expression in words, match expressions to stories and sort them by their terms.
New words
product · the answer to a multiplicationquotient · the answer to a divisionmore than / less than · words for + and − : “5 more than x” is x + 5
Explanation
We can say every expression in words. 5x is “5 times x” or “the product of 5 and x”. x + 5 is “x plus 5” or “5 more than x”. x − 5 is “5 less than x”. x ÷ 5 is “x divided by 5” or “the quotient of x and 5”. Take care: 3x means 3 times x, not 3 and x written side by side. If x = 4, then 3x = 12, and not 34. We can also sort expressions by how many terms they have: 3x has one term, x + 2 has two terms, and 3x + y + 1 has three terms.
| In words | Expression |
|---|---|
| 5 times x | 5x |
| 5 more than x | x + 5 |
| 5 less than x | x − 5 |
| x divided by 5 | x ÷ 5 |
Worked examples
| n | 1 | 2 | 5 |
|---|---|---|---|
| 4n + 3 | 7 | 11 | 23 |
| Terms | Expressions |
|---|---|
| one | 7, 3x, 9y |
| two | x + 2, 5y + 1 |
| three | 2a + b + 4 |
| p | 3p | 3 and p side by side (wrong) |
|---|---|---|
| 4 | 12 | 34 |
| 10 | 30 | 310 |
Class activity
Say it two ways. A grown-up writes an expression such as 2x + 7. The child says it in words two different ways, then makes up a story for it. Swap roles with an expression like n − 3. Check that the order in “less than” is right.
Practice
1
Say 6a in words.
“6 times a” or “the product of 6 and a”.
2
Say a + 6 in words.
“a plus 6” or “6 more than a”.
3
How many terms does 8x + 2y + 1 have? List them.
Three terms: 8x, 2y and 1.
4
Sort into “one term” and “more than one term”: 5, 2x, x + 9, 4y, 3x + y.
One term: 5, 2x, 4y. More than one: x + 9 and 3x + y.
5
If x = 5, what is 3x? A friend says 35. What is wrong?
3x = 3 × 5 = 15. The friend wrote 3 and 5 side by side instead of multiplying.