Question

Enter a number in the box to complete the sentence. Give your answer to the nearest half-hour.

When lit, a candle loses 5% of its original height every hour. Jennifer lit a candle with an original height of 8 inches.
Until the candle has been burning for at least _____ hours, the height of Jennifer's candle will be more than 7 inches.
Please help me answer this I'm currently taking the end of the year assessment right now!!

Answer 1

2.5

Explanation:

I had this question and got it right

Answer 2

2.5 hours

Explanation:

To solve this question we can use the exponencial function:

P = Po * (1 + r)^t

Where P is the final value, Po is the inicial value, r is the rate and t is the time.

In this case, we have Po = 8, P = 7 and r = -5% = -0.05. So, we can solve for t:

7 = 8 * (0.95)^t

0.95^t = 0.875

log(0.95^t) = log(0.875)

t * log(0.95) = -0.1335

t * (-0.0513) = -0.1335

t = -0.1335 / (-0.0513) = 2.6023 hours

Rounding to the nearest half-hour, we have t = 2.5 hours