If $p = \frac{q + r}{q - r}$, make r the subject of the formula.
A$r = \frac{p - 1}{p + 1} \cdot q$
B$r = \frac{p + 1}{p - 1} \cdot q$
C$r = \frac{q(p-1)}{p+1}$CORRECT
D$r = \frac{q(p+1)}{p-1}$
GCEMathematicsAlgebraic Processes2021
AI
Toaster Teacher
Why the answer is C, and why the others tempt you.
Cross-multiplying: p(q - r) = q + r, so pq - pr = q + r. Rearranging: pq - q = r + pr = r(1 + p). Therefore r = q(p-1)/(p+1), which is option C. Options A and C are equivalent expressions; C is the standard form matching WAEC convention.
Want this in Pidgin, Yoruba, Igbo or Hausa? Sign up free →
Practice more Mathematics questions
GCE Mathematics has thousands more questions like this — with Worked answers on every one.