Section B ( 40 marks )
7 . The insurance cost of an electric car depends partly on the distance it has travelled . The following table shows the distance and the insurance costs for five electric cars on 1 January 2021 .
Travelling distance ( x km ) |
20000 |
25000 |
30000 |
35000 |
40000 |
Insurance cost ($ y ) |
12000 |
10800 |
9600 |
9000 |
8500 |
The relationship between x and y can be modelled by the regression equation y �ax � b .
( a ) Write down the value of a and of b .
On 1 January 2021 , Hyung Sik buys an electric car which has travelled 32500 km .
[ 2 ]
( b ) Use the regression equation to estimate the insurance cost of Hyung Sik ’ s electric car .
[ 2 ]
The insurance cost of an electric car decreases by 2.5 % each year .
( c ) Calculate the insurance cost of Hyung Sik ’ s electric car after 4 years .
[ 4 ] Hyung Sik will buy an extra electric car when the insurance cost of his original electric car reaches $ 6500 .
( d ) Find the year when Hyung Sik buys an extra electric car . [ 4 ]
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