First algebra and simple equations · Usually met around P5
Words into algebraic expressions
Brackets round the part done first.
How to do it
Method
Brackets round the part done first
x plus 2, then times 3 → 3(x + 2)
Another way
Check with a number
x = 1: (1 + 2) × 3 = 9 but 3 × 1 + 2 = 5
In full
Find the unknown and give it a letter, then turn the words into operations piece by piece: “5 more than x” is x + 5, “5 less than x” is x − 5, “5 times x” is 5x, “x shared into 5” is x ÷ 5. A part done first needs brackets: “x plus 2, then times 3” is 3(x + 2), not the same as “3 times x, plus 2”, 3x + 2. Check by trying a number in the expression and seeing if it matches the words.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
Which expression means “9 more than x”?
- A. x − 9
- B. x + 9
- C. 9x
- D. 9 − x
Choose the right answer
Show the answer and working
Answer: B. x + 9
9 more is plus 9: x + 9.
Example 2
“7 times x, minus 10” as an expression is □x − □.
Fill in each box
Show the answer and working
Answer: 7，10
7 times x is 7x; minus 10: 7x − 10.
Example 3
Which expression means “a divided by 4, then plus 14”?
- A. 4 ÷ a + 14
- B. a ÷ 4 + 14
- C. (a + 14) ÷ 4
- D. a ÷ (4 + 14)
Choose the right answer
Show the answer and working
Answer: B. a ÷ 4 + 14
Divide, then add, which is the usual order: a ÷ 4 + 14, no brackets needed.
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