SOLUTION: Please help me solve this problem? "Bob cycles along a road He cycles 60km at an average speed of xkm/h He then cycles a further 45km at an average speed of (x+4)km/h His t

Algebra ->  Human-and-algebraic-language -> SOLUTION: Please help me solve this problem? "Bob cycles along a road He cycles 60km at an average speed of xkm/h He then cycles a further 45km at an average speed of (x+4)km/h His t      Log On


   

Question 920429: Please help me solve this problem?
"Bob cycles along a road
He cycles 60km at an average speed of xkm/h
He then cycles a further 45km at an average speed of (x+4)km/h
His total cycling time was 6h"
"Form an expression in terms of x and show that it simplifies to 2x%5E2-27x-80"
Found 2 solutions by ewatrrr, richwmiller:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
60km%2Fx+%2B+45km%2F%28x%2B4%29+=+6hr |Multiplying thru by x(x+4) so as all denominators = 1
60(x+4) + 45x = 6x(x+4)
60x + 240 + 45x = 6x^2 + 24x
6x^2 - 81x - 240 = 0
2x^2 + 27 - 80 = 0
.......
..........
x+=+%28-27+%2B-+sqrt%28+1369%29%29%2F%284%29+
x+=+%28-27+%2B-+37%29%2F%284%29+
x = -16, x = 10/4 = 5/2 = 2.5

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
a+b=6
r*t=d
t=d/r
a=60/x
b=45/(x+4)
60/x+45/(x+4)=6
(15(7x+16))/(x(x+4)) = 6
(2x+5)(x-16)=0
2x^2 -27x -80