Question

A candle has been burning for 20 min and is now 25 cm tall. In an hour it will be 10 cm tall. Which equation models the height y of the candle in centimeters, x minutes after it was lit?

Answer 1

Answer:

(y - 25) = - 0.25(x - 20)

Step-by-step explanation:

Given that :

Height of candle after burning for 20 minutes = 25 cm

Height after burning for 1 hr (60 minutes) = 10 cm

Height (y) in cm of candle x minutes after being lit:

Using the equation :

(y - y1) = m(x - x1)

m = (change in y / change in x)

Change in height within 60 minutes :

Height at 20 minutes = 25cm

Height after an hour = 10

Change in height per hour = (25 - 10) = 15cm

Hence, m = change in height per minute

15cm / 60 = 0.25cm ( - 0.25) (decrease in height)

y1 = 25 ; x1 = 20

(y - y1) = m(x - x1)

(y - 25) = - 0.25(x - 20)