Mark Scheme (Results) Summer 2009

Transcription

1 Mark Scheme (Results) Summer 009 GCSE GCSE Mathematics (Linear) Paper:

2 NOTES ON MARKING PRINCIPLES 1 Types of mark M marks: method marks A marks: accuracy marks B marks: unconditional accuracy marks (independent of M marks) Abbreviations cao correct answer only ft follow through isw ignore subsequent working SC: special case oe or equivalent (and appropriate) dep dependent indep - independent 3 No working If no working is shown then correct answers normally score full marks If no working is shown then incorrect (even though nearly correct) answers score no marks. 4 With working If there is a wrong answer indicated on the answer line always check the working in the body of the script (and on any diagrams), and award any marks appropriate from the mark scheme. If working is crossed out and still legible, then it should be given any appropriate marks, as long as it has not been replaced by alternative work. If it is clear from the working that the correct answer has been obtained from incorrect working, award 0 marks. Send the response to review, and discuss each of these situations with your Team Leader. If there is no answer on the answer line then check the working for an obvious answer. Any case of suspected misread loses A (and B) marks on that part, but can gain the M marks. Discuss each of these situations with your Team Leader. If there is a choice of methods shown, then no marks should be awarded, unless the answer on the answer line makes clear the method that has been used. 1380_4H

3 Follow through marks Follow through marks which involve a single stage calculation can be awarded without working since you can check the answer yourself, but if ambiguous do not award. Follow through marks which involve more than one stage of calculation can only be awarded on sight of the relevant working, even if it appears obvious that there is only one way you could get the answer given. 6 Ignoring subsequent work It is appropriate to ignore subsequent work when the additional work does not change the answer in a way that is inappropriate for the question: e.g. incorrect canceling of a fraction that would otherwise be correct It is not appropriate to ignore subsequent work when the additional work essentially makes the answer incorrect e.g. algebra. Transcription errors occur when candidates present a correct answer in working, and write it incorrectly on the answer line; mark the correct answer. 7 Probability Probability answers must be given a fractions, percentages or decimals. If a candidate gives a decimal equivalent to a probability, this should be written to at least decimal places (unless tenths). Incorrect notation should lose the accuracy marks, but be awarded any implied method marks. If a probability answer is given on the answer line using both incorrect and correct notation, award the marks. If a probability fraction is given then cancelled incorrectly, ignore the incorrectly cancelled answer. 8 Linear equations Full marks can be gained if the solution alone is given on the answer line, or otherwise unambiguously indicated in working (without contradiction elsewhere). Where the correct solution only is shown substituted, but not identified as the solution, the accuracy mark is lost but any method marks can be awarded. 9 Parts of questions Unless allowed by the mark scheme, the marks allocated to one part of the question CANNOT be awarded in another. 10 Money notation Accepted with and without the p at the end. 1380_4H 3

4 1 (a) M1 for seen or digits 46 A1 for 46, accept 46.00, 46.0 (b) M1 for seen or digits 78 A1 for 78, accept 78.00, 78.0 (a) Correct shape B for correct shape; any orientation. (B1 for any two sides correct or all correct for scale factor other than 1 or ), tolerance to within half square (b) Reflection in line x = 0 B1 for reflection, reflect, reflected. B1 for line x = 0 or y-axis NB: more than one transformation should be awarded 0 marks ,, 10 M1 for 1 +1 or +1 or 3 +1 (but not 1 +1, +, 3 +3) A1 for,, 10 SC: B1 for 1,, with or without working 4 (a) (6, 100), (80, 110) plotted 1 B1 for plotting both points (6, 100), (80, 110) correctly (tolerance one square); ignore any additional plots given. (b) positive (correlation) 1 B1 for positive (correlation) or length increases with height oe (c) M1 for a single line segment with positive gradient that could be used as a line of best fit or a vertical line from 76 A1 for given answer in the range _4H 4

5 = = M1 for (or 7.6 seen) or (or seen) M1(dep) for or or A1 for cao accept 34.36p Alternative method: 31 M1 for (or 1.63(1 ) seen) 19 M1 (dep) A1 for cao accept 34.36p 6 (a) M1 for or or or seen 7 seen or A1 for 17.6 or 88 or oe (b) 68 = 1.8C C = 68 3 C = M1 for 68 3 or 36 or 68 = 1.8C + 3 seen; condone replacement of C by another letter. A1 for 0 cao NB Trial and improvement score 0 or 7 diagram 3 M1 for line drawn or point marked within guidelines from P M1 for line drawn or point marked within guidelines from Q up to top guideline from P A1 for point indicated within region where guidelines intersect 1380_4H

6 8 (a) 18 6 :1 6 3 : M1 for 18 : 1 or 1 : 18 or 1.:1 oe or any correct ratio reversed eg :3 A1 for 3 : or 1 : 0.6 [recurring] (b) + 1 = = M1 for or or 4 +1 or 4 or 70 or 9 : 4 or 9 seen, as long as it is not associated with incorrect working. A1 for 4 cao (6).6 69.(76).7 73.(683) (09) (79) (84) (91) (99).66 7.(01) (34) (48) (6).6 4 B for trial.6 x.7 evaluated (B1 for trial x 3 evaluated) B1 for different trial.6 < x.6 B1(dep on at least one previous B1) for.6 Values evaluated can be rounded or truncated, but to at least sf when x has 1dp and 3sf when x has dp NB Allow 7 for evaluation using x =.66 NB No working scores no marks even if answer is correct 10 construction M1 for arcs from same centre on lines at same distance from meeting point (± mm) A1 for bisector (± o ) and correct arcs SC: B1 for bisector ( ± ) with no arcs, or incorrect arcs if M0 awarded. Accept bisectors that are dashed or dotted. 1380_4H 6

7 11 + prime number is odd M1 for a counter example showing intent to add and another prime number; ignore incorrect examples A1 for a correctly evaluated counter example with no examples given that involve either non-primes or incorrect evaluation Alternative method B for fully correct explanation is a prime number, odd + even (or ) = odd oe with no accompanying incorrect statements or examples (B1 for is a prime number or recognition that not all prime numbers are odd or odd + even (or ) = odd; ignore incorrect examples or statements) = = = = = = = M1 for fx consistently within interval including ends (allow 1 error) M1 (dep) consistently using appropriate midpoints M1 (dep on first M) for Σfx Σf A1 for with no arithmetic errors 1380_4H 7

8 13 ( ) M for (0. π 8) or π 4 or (π 8 + 8) or (0. x π 8 + 8) oe (M1 for π 8 or π 4; for a value.1-. inclusive unless seen with incorrect working eg πr ) A1 for (SC: B if M0 scored for ) 14 (a) a 3 1 B1 for a 3 cao (b) 3x 1x 10 1 B1 for 1x 10 cao (c) 3y y+ 3y 4 3y +1y M1 for 3y y+ 3y 4 or 3y + a or 3y +ay or b + 1y or by +1y where a,b are integers, and can be zero A1 for 3y +1y or 3 y + 1 y NB: If more than terms in expansion MOA0 (d) x 8+ 3x+ 6 x M1 for x 4 or x 8 or 3 x + 3 or 3 x + 6 A1 for x cao (e) x + 4x 3x 1 x + x 1 M1 for 4 terms correct with or without signs, or 3 out of no more than 4 terms, with correct signs (the terms may be in x x x 3 or an expression or table) or ( ) ( ) x ( x + 4) 3( x + 4) A1 for x + x 1 cao = = = M1 for or or or 3.73 or 10.4 or 8.4 seen A1 for.6(41); accept _4H 8

9 16 (a) 6 t + t B1 for t or for t + (b) 8 3 m m 1 B1 for m or for (c) 3 3 x 8x 3 B for 8x 3 cao (B1 for ax 3, a 8 or x x x or 8x n n 0,3) 8 3 m (d) a h = a h 7 B for 1a h 7 n (B1 for 1ah, n 0, or 1 m 7 a h, m 0,7 or ka h, k or 3 4 a h ) M1 for 9 6 or or 4 or 9 = AB + 6 oe M1 for or 4 A1 for [SC: M1 for or 117 ] 18 (a) Heaviest bag is 9kg 1 B1 for 3kg is the upper quartile oe, or the heaviest bag is 9kg oe, or % of bags are heavier than 3kg or range is 9 oe (b) 17 1 B1 for 17 cao (c) B1 for 13 cao (d) M1 for oe or oe A1 for 60 cao (SC: B1 for % or 0. or quarter seen) 1380_4H 9

10 19 (a) M1 for or for or for 4680 or 180 or 360 or 4860 M1 (dep) or for A1 for 4867.(0) cao (If correct answer seen then ignore any extra years) Alternative method M for or A1 for 4867.(0) cao [SC: 367.(0) seen B] (b) n M1 for an attempt to evaluate n for at least n one value of n (not equal to 1) or (n ) n or (= ) and 1.07 evaluated, n 400 A1 for cao 1380_4H 10

11 0 (a) cos x = M1 for cos( x = ) M1 for cos or cos 0.6, or cos -1 ( 8) 8 A1 for (SC B for or seen) 1 Alternative Scheme h = 8 (=39) "39" M1 for sin(x=) 8 sin x sin 90 = oe or "39" 8 ( "39") = 8 + or tan (x=) 8 cos x "39" or "39" M1 for sin 1 "39" sin 90 ( ) or sin 1 ( ) or 8 8 "39" tan ( "39") ( ) or cos ( ) 8 A1 for _4H 11

12 (b) tan 40 = y y M1 for tan 40 = y = 1. tan 40 M1 for 1. tan 40 A1 for SC: B for ±( ) or seen Alternative scheme y 1. M1 for = oe sin 40 sin 0 1. M1 for y = sin 40 sin 0 A1 for SC: B for ±(3.4 3.) or seen 1 (a) a 8 M1 for 0 or 0 oe, a < 8 or.03(8 ) or 8 a 6.16 A1 for cao (b) ( ) ( + + ) or 8 M1 for or oe or 6.1(6 ) or or A1 for 6 or _4H 1

13 1n 3 ( 9n + 6n+ 1) M1 for (3n) + 3n + 3n + 1 or (3n) 3n 3n + 1 or correct comment ( 9n 6n+ 1) = 1n (( 3n+ 1) ( 3n 1) ) ( 3n+ 1) + ( 3n 1) ( ) A1 for 1n from correct expansion of both brackets A1 for 1n is a multiple of 4 or 1n = 3 4n or 1n 1n 1n = 4 3n or = 3n or = 4n 4 3 NB: Trials using different values for n score no marks. 3 (a) b a 1 B1 for b a or a + b oe (b) OP = OA + AP proof 3 M1 for OP = OA + AP oe or OP OB + BP = oe OP = a + 3 (b a) 3 M1 for AP = x (b a) oe or BP = x (a b) oe OP = 1 (a + 3b) A1 for a + 3 x (b a) oe or b + x (a b) oe leading to given answer with correct expansion of brackets seen 1380_4H 13

14 sin60 M1 for sin60 or for or π or or ±.48(6...) 60 M1 for 3 = π (= 4.71 ) M1(dep on 1 previous M1) for area of triangle area of sector A1 for SC: B3 for or ( x 3) ( x ) ( x+ 3) ( x ) ( x 3) ( x + 3) 3 B1 for ( x 3)( x ) or x ( x ) 3( x ) M1 for ( x ± 3)( x ± ) or x( x + ) ± 3( x + ) or x ( x ) ± 3( x ) ( x 3 ) A1 for cao as final answer x + 3 ( ) 1380_4H 14

15 a b M1 for at least one product of the form M1 for identifying all products (condone errors in 6 products, 1 error in 3 products) + + Either ,,,,, or or ,, or or,, M1 (dep) for ' ' oe or ' + + ' oe or 1 ' + + ' oe A1 for 131 oe or correct to at least decimal places 190 or answer that rounds to 0.69 NB : If decimals used for products then must be correct to at least decimal places 1380_4H 1

16 With replacement M0 M1 for identifying all products (condone errors in 6 products, 1 error in 3 products) either ,,,,, ,, or ,, or M1 (dep) for ' ' or ' + + ' or 1 ' + + ' A0 for 6 6 oe or 0.6 (NB: oe or 0.6 implies M) Partial replacement SC: B for oe or 0.70 or oe or correct to at least decimal places 1380_4H 16