110k views
4 votes
A. A candle begins burning at time t = 0. Its original

height is 12 in. After 30 min the height of the candle is
8 in. Draw a graph showing the change in the height of
the candle.
b. Write an equation that relates the height of the candle
to the time it has been burning.
c. How many minutes after the candle is lit will it burn out?

2 Answers

1 vote

Answer:

a) draw with intersecting points (0, 12) and (30,8)

b) y=-4/30x+12

c) 90

Explanation:

a) First, we need to find 2 points on the graph in order to make a line. We can see that one point will be (0, 12). This is because the time will represent x and the height will represent y. The next point we can find is (30, 8).

b) We can find the equation by first finding the slope. We can do this by subtracting (38-12)/(30-0). This gets us -4/30.

Then we can find the y-intercept. We can do this by imputing one of the coordinates into our equation so far, y=-4/30x+b. However, we already have a point with an x-coordinate of 0, so doing so will not be necessary. The y-intercept, or b, is 12.

We can now put our equation together, and it will be y=-4/30x+12.

y can also be replaced with h for height, and x can be replaced with t for time.

c) We can solve for this by making the height (y or h) 0. We can plug this into the equation to get 0=-4/30*x+12. Then we can solve for it using algebra.

0=-4/30x+12

4/30x=12

x=(12/1)*(30/4)

x=360/4

x=90

User Chandan Nayak
by
7.4k points
0 votes

Answer: C. 90min

Explanation:

Candle burns at the rate of 4 in per 30 min so 12 in would burn in= 30 x 12/4= 90 min.

0 min= height: 12 in

30 min= height: 8 in

60 min= height: 4 in

90 min: height: 0 in

Hope this helps.

User Nitneq
by
8.0k points