The table shows experimental values of variables x and y. X | 5 | 30 | 150 | 400 y | 8.9 | 21.9 | 48.9 | 80.6
- (i)By plotting a suitable straight line graph, show that y and x are related by the equation y = axᵇ, where a and b are constants.[4]
- (ii)Use your graph to estimate the value of a and of b.[2]
- (iii)Estimate the value of y when x = 100.[2]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2012). The mark or mark type is shown in brackets.
- [B1] (i) ln y = ln a+b ln x OR lg y = lg a + b lg x may be implied
- [M1] (i) Plot ln y / lg y against ln x / lg x with attempt at linear scale
- [A2, 1, 0] (i) (Marks for points and line on graph NOT for table)
- [M1] (ii) Calculates gradient of straight line log graph
- [A1] (ii) b = 0.5±0.03
- [M1] (ii) Intercept is ln a or lg a on straight line log graph
- [A1] (ii) a = 4±0.3
- [M1] (iii) Uses suitable graph or formula
- [A1] (iii) 32 to 49
Write your answer and get it marked
On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.
Sign up free →