i need some help with these two quadratic problems:
- A family drives 240 km to their cottage. They can save fuel by reducing their average speed by 20 km/h and this will mean that the trip will take one hour longer. What is this lower average speed?
- JB bought some balls for $600. If the cost for each ball had been 25 cents less, she would have had 10 more balls for her $600. How much did she pay for each ball.
can you help me set up the equation?
thank you for your expertise (Emo)
let time= x hr
time speed= 240/x km/hr
new speed= (240/x)-20 kn/he
new time= x+1 hr
but distance is same = 240 km
x=3 or -4
time =3 hr.
initial speed = 80 km/hr
new lower speed =(80-20)km/hr=60 km/hr.
i guess thats the answer?
quadratic problem #1
thanks so much
I set up a ratio but it kept coming out wrong :o
total money= $600
let no. of balls bought =x
cost of each ball = $600/x
new cost = $((600/x)-0.4)
no. of balls bught at reduced rate= 600/new cost.
new number of balls bought=x+10
u do the rest.
and thanks for the thanks.
something went wrong!
i can see how this makes sense but when I do it, the x works out to 6, which makes them going pretty slow!
240 = 240x/x - 20x + 240/x - 20x
the x cancels
240 = 240 - 40x + 240/x
multiply by x to get rid of denominator
240x = 240x - 40x^2 + 240x
0 = -40x^2 + 240x
using quadratic formula
c=0 (can c equal 0?)
- 240 +- sq root 240^2 - 4*-40*0/ 2(-40)
- 240 +- 240 / -80
- 480/ -80
what did I do wrong?
x is the time taken. so now u will have to calculate speed = d/t
and c can be zero.