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# Level 3-4 Algebra - Putting Numbers in Place of Letters

You've probably figured out by now that algebra is a big player in KS3 Maths. In algebra, instead of numbers, we use letters like a and b. When these letters stand for unknown numbers, we call them variables. But sometimes, we know the numbers they represent – and that's where equations come in.

1.
If a = 2 and b = 3, what is the value of a + b + a?
5
6
7
8
2 + 3 + 2 = 7
2.
If x = 2 and b = 4, what is the value of x2 + b2?
12
16
20
24
(2 x 2) + (4 x 4)
3.
If a = 6 and x = 8, which of the following gives a value of 22?
a + x2
a + 2x
2a + 2x
2ax
'If in doubt, write it down and work it out'
4.
If x = 9 and y = 23, what is the value of y - x?
14
16
18
20
23 - 9 = 14
5.
If a = 2, b = 3, c = 4 and d = 5, what is the value of 2a + 3b + c2 - d
24
26
28
30
4 + 9 + 16 - 5 = 24. Don't forget 'IF IN DOUBT, WRITE IT DOWN AND WORK IT OUT!
6.
If x = 5 and y = 10, what is the value of xy / 10
3
5
10
20
Two letters together need to be multiplied together
7.
If a = 4 and b = 2, what is the value of a2 / b?
8
16
4
2
16 / 2 = 8
8.
If a = 4 and b = 5, what is the value of 2a + b
7
9
11
13
Remember that when a number and a letter are together they need to be multiplied together
9.
If a = 4 and b = 8, what is the value of 2a + x2
64
75
80
It is impossible to say
Notice that we did not give you a value for x and therefore you cannot work out the expression!
10.
If x = 6 and y = 7, which of the following gives a value of 55
x2 + y2
xy2
x + y2
2x + 2y
You can make an estimate before you find the right answer. x2 + y2 would be too high, as would xy2. You can then check the other two more likely answers
You can find more about this topic by visiting BBC Bitesize - Writing and interpreting algebraic expressions

Author:  Frank Evans