Substituting into formulae

A formula connects quantities: v = u + at gives the speed v after time t.

Replace each letter with its value, in brackets, then use the order of operations.

1. v = u + at, u = 4, a = 2.5, t = 6
2. v = 4 + 2.5 × 6
3. = 4 + 15 = 19

Multiplication happens before addition, so 4 + 2.5 × 6 is not 6.5 × 6.

• E = ½mv²: only v is squared. With m = 10 and v = 4: ½ × 10 × 16 = 80.
• A = ½(a + b)h: the bracket first, then halve and multiply.
• r = √(A/π): divide inside the root first. Use the calculator's π key and keep all the digits until the end.

Work out (4/3) × π × 2.5³ in one go, then round to 3 significant figures. Then work out √(150 ÷ π). Check that brackets go round the whole of A/π.