Using a formula II 0 Overview Using this Resource Connecting to the Curriculum Marking Student Responses Working with Students Further Resources This task is about using algebraic formulae to solve maths problems. Question 1Change answer a) Lucy is a plumber. She charges a call-out fee of $45 and $35 each hour after that. She uses the following formula to work out her charges: C = 45 + 35h where h = number of hours worked and C = total amount charged ($) a) Lucy is a plumber. She charges a call-out fee of $45 and $35 each hour after that. She uses the following formula to work out her charges: C = 45 + 35h where h = number of hours worked and C = total amount charged ($) If Lucy worked for 4 hours how much would she charge? Total amount charged = $ Question 1Change answer b) Wiki dropped a ball from near the top of the Eiffel Tower. The distance travelled can be described by this formula: S = 5t 2 where t = time taken to reach the ground (s) and S = distance travelled (m) b) Wiki dropped a ball from near the top of the Eiffel Tower. The distance travelled can be described by this formula: S = 5t 2 where t = time taken to reach the ground (s) and S = distance travelled (m) If the time taken for the ball to reach the ground was 7 seconds, how far had the ball travelled? Distance travelled = m Question 1Change answer c) Sam was working out how much money he had in his savings account after one year. The total amount in his account after one year can be shown by the formula: where i = interest rate (%) T = total amount in his account after one year ($) and 400 = amount in his account at the beginning of the year ($). c) Sam was working out how much money he had in his savings account after one year. The total amount in his account after one year can be shown by the formula: where i = interest rate (%) T = total amount in his account after one year ($) and 400 = amount in his account at the beginning of the year ($). If the interest rate over the year was 15%, how much would be in Sam's account at the end of one year? Total amount after one year = $ Task administration: This task is completed with pencil and paper or online (WITH automarking). Level: 5 Curriculum info: Maths, Number and Algebra, Equations and expressions Keywords: algebraic expressions, equations, substitution Description of task: Students solve given algebraic expressions using substitution. Answers/responses: Y10 (08/2001) a) 185 easy b) 245 moderate c) 460 moderate Diagnostic and formative information: Common error Likely miscalculation Likely reason a) $150 Excludes the call-out fee of $45. b) 1225 49 35 52 × 72 72 5 × 7 Squares the 5 before multiplying. Excludes multiplying '5'. Does not square the 7. c) 60 Excludes the initial amount in account of $400. Velocity and force formulae Ziggurat formula Length, area and algebra
