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changes from 45 'to 30°.find the height of the tower. (4)(b) By increasing the speed of a car by 10km/h, the time of journey for a distance of 72 km is reducedby 36 minutes .Find the original sped of the car. (3) |
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Answer» Let the speed of the car be xtime taken to cover 36 km = 36/x hrATQ36/x - 36/(x+10) = 18/60(36(x+10) - 36x)/x(x+10) = 3/10(36x + 360 - 36x)/(x^2+ 10x) = 3/10360x10 = 3(x^2 + 10x)3x^2 + 30x = 36003x^2 + 30x - 3600= 0x^2 + 10x - 1200=0x^2 + 40x - 30x - 1200=0x(x+40) - 30(x+ 40)= 0(x-30)(x+40)=0we get 2 answersBut x=30 is the correct onetherefore the speed of the car is 30 km/hr |
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