Moderate -0.8 This is a straightforward algebraic rearrangement requiring expansion of brackets, collecting like terms, and factorising to isolate c. It's simpler than average A-level content as it involves only basic algebraic manipulation with no problem-solving or conceptual depth, though it does require careful handling of terms.
Question 9:
9 | 5c + 9t = 2ac + at
5c 2ac = at 9t oe
c(5 2a) = at 9t oe
at 9t t(a 9)
c or oe as final answer
5 2a 5 2a | M1
M1
M1
M1
[4] | for correct expansion of brackets
for correct collection of terms, ft
eg after M0 for 5c + 9t = 2ac + t allow this
M1 for 5c 2ac = 8t oe
for correctly factorising, ft; must be
c × a two-term factor
for correct division, ft their two-term factor | for each M, ft previous errors if their
eqn is of similar difficulty;
may be earned before t terms collected
treat as MR if t is the subject, with a
penalty of 1 mark from those gained,
marking similarly