Rearranging Formulas Flashcards

All 7 cards in this deck

What does it mean to make a variable the subject of a formula?

Rearrange the formula so that variable is on its own on one side of the equals sign, and does not appear on the other side.

What are the steps to make a variable the subject of a two-step formula?

e.g. make $v$ the subject of $T = 4v + 3$

1. Undo the $+$ or $-$ first: $T - 3 = 4v$
2. Divide both sides by the coefficient: $\frac{T-3}{4} = v$
3. Write the subject first: $v = \frac{T-3}{4}$

What are the steps to make a variable the subject when it is inside a fraction?

e.g. make $h$ the subject of $p = \frac{h-5}{3}$

1. Multiply both sides by the denominator: $3p = h - 5$
2. Undo the $+$ or $-$: $3p + 5 = h$
3. So $h = 3p + 5$

How do you make a letter the subject when it is inside a bracket?

e.g. make $x$ the subject of $y = 3(x+2)$

Divide both sides by the number outside the bracket (or expand first), then undo what is left: $x = \frac{y}{3} - 2$.

What are the steps to use a formula to find the value of a letter that is not the subject?

e.g. $P = 2g + 4h$; find $g$ when $P = 38$ and $h = 3$

1. Make that letter the subject: $g = \frac{P - 4h}{2}$
2. Substitute the values: $g = \frac{38 - 12}{2}$
3. Work it out: $g = 13$

What are the steps to make a letter the subject of a formula when it is squared?

e.g. make $x$ the subject of $y = x^2 + 1$

1. Get the squared term alone: $y - 1 = x^2$
2. Square root both sides: $x = \pm\sqrt{y - 1}$

How do you make a letter the subject when it is inside a square root?

e.g. make $x$ the subject of $y = \sqrt{x - 4}$

Square both sides, then rearrange: $x = y^2 + 4$