Mixed modelling and checking · Optional extension
L092 · Allow 10–15 minutes for learners ready to move on. Answers are available after an attempt.
Stretch
A phone plan costs £12 plus 8p per text. Write a formula and find the cost for 125 texts.
Reveal a worked check after attempting
C=12+0.08t; C(125)=£22.
Deep challenge
A rectangle has perimeter 40 cm. Express area in terms of width x and find width for length 12 cm.
Reveal a worked check after attempting
Length=20−x, area=x(20−x); if length 12, width=8 cm.