Edexcel Mathematics Higher Tier, November 2009 (1380/4H) (Paper 4, calculator)


Question 19 a)


(x – 3)(x + 5) = x2 – 15 + 5x – 3x = x2 + 2x - 15


b) multiply both sides by 4 29 – x = 4(x + 5) expand the RHS 29 – x = 4x + 20 add x to both sides 29 = 5x + 20 subtract 20 from both sides 9 = 5x rewrite 5x = 9 divide both sides by 5 x = 1.8


Now you should put this value of x back into the original equation to check = 1.8 + 5 the LHS equals 6.8 and the RHS equals 6.8 )


( – . 


Question 20 a) to work out the four point moving average simply add up the 4 points and divide by 4. (if it were a 3 point moving average we would add 3 points and divide by 3).


 


=   = £90


b) The moving averages are steadily increasing which means that the cost of gas used by a family increases over time. (By using moving averages we are smoothing out any seasonal variations.)


Question 21 If we think of the original as being 100%, then after a reduction of 12% we would have 88%. The sale price of the camera represents 88%. We want to find out what 100% would be (ie the normal price)


First find 1% by dividing by 88 then scale up to get 100%


. 


x 100 = £151 www.chattertontuition.co.uk 0775 950 1629 Page 9


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