please help me answering this
Attachments:
steeve:
hint : let the speed of the plane in still air be x km/h , then 3600/(x-30) - 3600(x+30) = 2/3
Answers
Answered by
1
Continuation of your answer:
3600/(x - 30) - 3600/(x + 30) = 2/3
LCM = 3(x - 30)(x + 30).
3600/(x - 30) * 3(x - 30)(x + 30) - 3600/(x + 30) * 3(x - 30)(x + 30) = 2/3 * 3(x - 30)(x + 30).
3600 * 3 * (x + 30) - 3600 * 3 * (x - 30) = 2(x - 30) * (x + 30)
10800(x + 30) - 10800(x - 30) = 2(x^2 - 900)
10800x + 324000 - 10800x + 324000 = 2x^2 - 1800
648000 = 2x^2 - 1800
2x^2 = 649800
x^2 = 649800/2
x^2 = 324900
x = 570 (or) - 570.
Since x cannot be -ve, so x = 570.
Therefore the speed of the plane = 570.
Hope this helps!
3600/(x - 30) - 3600/(x + 30) = 2/3
LCM = 3(x - 30)(x + 30).
3600/(x - 30) * 3(x - 30)(x + 30) - 3600/(x + 30) * 3(x - 30)(x + 30) = 2/3 * 3(x - 30)(x + 30).
3600 * 3 * (x + 30) - 3600 * 3 * (x - 30) = 2(x - 30) * (x + 30)
10800(x + 30) - 10800(x - 30) = 2(x^2 - 900)
10800x + 324000 - 10800x + 324000 = 2x^2 - 1800
648000 = 2x^2 - 1800
2x^2 = 649800
x^2 = 649800/2
x^2 = 324900
x = 570 (or) - 570.
Since x cannot be -ve, so x = 570.
Therefore the speed of the plane = 570.
Hope this helps!
Similar questions