Slides in this set
We often use formulae without even
noticing. For example, we might convert
miles to km by multiplying by 1.6, or find the
circumference of a circle by multiplying pi by
km = 1.6 x miles is an example of a formula.
We have already seen that km = 1.6 x miles and
C = × d are examples of formulae. There are
many others that we use regularly in other
Changing the subject of a formula
The formula for finding the circumference of a
circle is C = 2r. So it is easy to find the
circumference if we know the radius.
What happens, though, if we know the
circumference but want to know the radius?
In this case we can rearrange to make r the
subject of the formula.…read more
In an equation, each letter stands for a missing number. To
solve an equation, find the values of the missing numbers.
The best way to solve an equation is by using 'inverses', or
undoing what the equation is doing.
To use this method to solve equations remember that:
adding and subtracting are the inverse - or opposite - of each
multiplying and dividing are the inverse of each other
When you use this method you must perform the same
action on both sides.
Solve the equation: x - 6 = 9
To get x on its own, we need to add 6. If you add 6 to one side
of the equation, you need to add 6 to the other side of the
x = 15…read more
Equations with brackets
If an equation has brackets in it, one method of solving it is to
multiply out the brackets first, for example:
Solve the equation: 3(b + 2) = 15
3(b + 2) = 15
Multiply out the brackets. Remember, everything inside the
brackets gets multiplied by 3.
3 × b + 3 × 2 = 15
When you have multiplied out the brackets you get: 3b + 6 = 15
Next, undo the + 6. In other words, do the inverse and subtract 6
from both sides.
3b + 6 - 6 = 15 - 6
So 3b = 9
Therefore, to find out what b is you need to do the inverse of
multiplying by 3 which is dividing by 3.
So b = 3…read more