Substitution

Description

Replace formulae and expressions with numerical values, including scientific formulae.

Example 1 $$y=mx+c$$ What is the value of y when m is 3, x is 4 and c is 5?

$$y=3(4)+5$$ $$y=17$$ Notice that we have replaced the letters with numbers but also maintained the multiplication between the m and $x$. We don't change $mx$ to 34!

Substitution is a core skill needed to be successful in the GCSE and you need to be comfortable with substituting into difficult equations too.

Example 2 $$s=ut+\frac{1}{2}at^2$$ What is the value of s when u is 4, t is 5 and a is 2? $$s=4(5)+\frac{1}{2}(2)(5)^2$$ $$s=20+25$$ $$s=45$$

Links

Manipulating algebraic fractions