Changing the subject with simple formula | Maths | Quizalize & Oak National Academy

Starter quiz

Division in the __________ operation of multiplication.
- improper
- inequal
- invariant
- inverse ✓
Select the rearrangements of the additive relationship 389.16 + 417.4 = 806.56.
- 417.4 + 389.16 = 806.56 ✓
- 806.56 + 417.4 = 389.16
- 417.4 − 806.56 = 389.16
- 806.56 − 417.4 = 389.16 ✓
- 417.4 − 389.16 = 806.56
Select the rearrangements of the multiplicative relationship $y=5x$ .
- $5y=x$
- ${5\over{y}}=x$
- ${y\over{5}}=x$ ✓
- ${y\over{x}}=5$ ✓
- ${x\over{y}}=5$
The solution to $x-13=63$ is $x=$ ______.
- '76' ✓
Laura begins to solve the equation $x-12=13$ by writing $x-12+12=13$ . What error has Laura made?
- Laura should add $13$ , not $12$ .
- Laura has only performed the operation $+12$ to one side of the equation. ✓
- The answer is obviously just $1$ . Laura doesn't need a method here.
- Laura should do $-12$ , not $+12$
Which of the below are rearrangements of the equation $17-x=2y$ ?
- $17+2y=x$
- $17=2y+x$ ✓
- $x-17=2y$
- $17-2y=x$ ✓
- $17-2x=y$

The __________ of a formula is a variable expressed in terms of other variables.
- solution
- subject ✓
- value
- variable
$y^2$ is not the subject of the equation $y^2=25-x^2$ . Why not?
- Because $y^2$ is not the solution.
- Because $x$ is the subject.
- Because the exponent of $y$ is not 1. ✓
- Because this is not an equation.
Match each equation to its subject.
- $c + d + e = f$
  
  ⇔
  
  $f$ ✓
- $c = f-(d+e)$
  
  ⇔
  
  $c$ ✓
- $c-d-f=e$
  
  ⇔
  
  $e$ ✓
- $d=c-ef$
  
  ⇔
  
  $d$ ✓
Laura wants to make $x$ the subject of the equation $x+3y=17$ . Which operation should she apply to both sides of the equation?
- $-17$
- $\div3$
- $-x$
- $-3y$ ✓
- $+3y$
Make $n$ the subject of $T=25-n$ .
- $n=25$
- $n+T=25$
- $n=T-25$
- $n=25-T$ ✓
- $n=T-25$
The formula for the volume of a cylinder is $V=\pi{r^2}h$ . Select the correct arrangement of the formula to make $h$ the subject.
- $V\pi{r^2}=h$
- ${V\over{\pi}r}=h^2$
- ${V\over{\pi}r^2}=h$ ✓
- $h={\pi{r^2}\over{V}}$
- ${V\over{h}}={\pi}{r^2}$

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Changing the subject can be thought of as solving an equation in one unknown.
Throughout the rearrangement, the expressions on each side of the equals sign remain equal.
Changing the subject can offer different perspectives on the relationship.
It can make it easier to calculate the unknown value if that is the subject.

The subject of a formula is just the first term in the formula.

Draw attention to the variety of equations and formulae used in the lesson.

Formula - A formula is a rule linking sets of physical variables in context. The plural of formula is formulae.
Subject - The subject of an equation/a formula is a variable that is expressed in terms of other variables. It should have an exponent of 1 and a coefficient of 1.