A 240 mm candle is burning and shrinks in height 5mm per second

240 - 5x and the candle will be at 0 mm in 48 seconds

Step-by-step explanation:

Step 1:  Convert words into an expression

A 240 mm candle is burning and shrinks in height 5mm per second

240 - 5x

Step 2:  If needed solve for x

240 - 5x - 240 = 0 - 240

-5x / -5 = -240 / -5

x = 48

 240 - 5x and the candle will be at 0 mm in 48 seconds

Graph Below:  (0, 240) shows the initial start and (48, 0) shows the ending point

step-by-step explanation:

part a. the differences are decreasing, so we know the sequence is not arithmetic. the ratios are constant (=3/4), so we know the sequence is geometric.

part b. from part a, we know the common ratio is 3/4, so each term is 3/4 of the one before. the initial term is the number of gallons at h=1.

g[h] = (3/4)·g[h-1]

g[1] = 384 . . . . initial value required for a recursive definition

part c. the general formula for a geometric sequence is

a[n] = a[1]·r^(n-1)

we have a[1] = 384, r = 3/4, and the term number given by h. the formula that follows is

g[h] = 384·(3/4)^(h-1)

part d. filling in the value and doing the arithmetic, we have

g[12] = 384·(3/4)^11 ≈ 384·0.042235136 ≈ 16.2183 . . gallons

part e. each gallon is 4 quarts, so

16.2183 gal × 4 qt/gal = 64.8732 qt