1981CEMCQ

13. Cost = Marked price - Profit = x - 0.3x =0.7x
Selling price = 0.8x
Profit = Selling price - Cost = 0.8x-0.7x = 0.1x

15 Volume increase ={ [ sq rt(1.44) ]^3 -1 } x 100% = 72.8%

17.Let the cost of each chair be $C.
Total cost =100C
Money acquired = 80 x 1.3 C + 20 x 0.6 C = 116C
Profit = 116C - 100C = 16C
% profit = 16c/100c x 100% = 16%

23.A line drawn in the figure // and equals to AB.
http://postimg.org/image/edykyaznd/
ED = p cosθ
DF = q sin∅
AB = ED + DF = p cosθ + q sin∅

29. 2x^2-2<=0
x^2-1<=0
(x+1)(x-1)<=0
The solution is -1<x<1

38. Average working efficiency of a worker = k/nx (watches/hr)
Let h hours be the new working hr for (x-y)workers work per day in order to produce k watches.
(k/nx)(x-y)h = k
(x-y)h =nx
h = nx / (x-y)

43. sinθ-cosθ=1/2
(sinθ-cosθ)^2=1/4
sin^2 θ - 2sinθcosθ + cos^2 θ = 1/4
1-2sinθcosθ = 1/4
sinθcosθ = 3/8

44. For 0<=θ<=360 , y = cos(θ/2) attains min at θ=360 , y=-1
So min of 1+2cos(θ/2) = 1+2(-1) = -1

45. that graph has problem , min of sinθ must <=1

49. that problem miss h

53. http://postimg.org/image/d36rljw91/

第49題應該係 let AB=h