Trial and improvement is where we guess what the answer could be and see if it works in the question. If it doesn’t work, then we guess a diff erent possible answer. We continue guessing and checking answers until we fi nd the right one.
Practice questions 9.1
1. Identify the variables and the constants in each of the following: (i) a = 5 + 12c (ii)
t = b + 5
(iii) f = m− 4d (iv) x = − 7 + 11y
2. Using the information below, create a formula in each case, given:
Value (total) = starting value + (rate of change × stage number)
Starting value
(i) (ii)
(iii) (iv) (v)
(vi) (vii)
(ix) (x)
4 2 7
–10 –50 –21 117
(viii) 1 024 –99 0
Rate of change
6 9
–3 2
–8 4
–34 –64 24
–59
Stage number
a v t
d n s r t
k x
Section A Introducing concepts and building skills 137
(v) k = 4g + 2 (vi) t = − 4 − 10p
(vii) θ = − 24 + 9e (viii) r = 5x− 7
(ix) β = 10y− 12 (x) d = − 6 − 23n
3. Copy the table provided and identify the starting value, rate of change and stage number in the following formulae.