After a gas-filled balloon is released, it rises 90 feet in the first minute. In the second minute, the balloon rises 120 feet, and in the third minute, it rises 150 feet. How many feet would the balloon rise in 8 minutes?

Question

anonymous · Answer

the answer is 300

rainbow_dash · Answer

thank you

anonymous · Answer

@jasonlam Just don't give the answer next time.

australopithecus · Answer

90, 120, 150

so we have points 

where x = minutes, y = feet
(1,90)
(2,120)
(3,150)

Use the equation of the line

y= mx + b

where 
m = slope
b = y-intercept

use the equation 

m = (y1-y2)/(x1-x2)
I'm using points (2,120) and (3,150)

120 - 90/3-2 = 30/1 = 30 = m


y = mx + b
plug in m
y = (30)x + b

solve for b by plugging in a point I used (1, 90)

y = 30x + b
90 = 30(1) + b
90-30 = b
60 = b
b = 30

so we have the equation
y = 30x + 60

checking the answer 

y = 30(1) + 60
y = 90

y = 30(2) + 60
y = 120

y = 30(3) + 60
y = 150

plug 8 into the equation, to find the amount of feet

australopithecus · Answer

hope this helps although I think you are done with this question ha