# Homework Help: Graphing an Exponential

1. Mar 21, 2006

### rachael

11 A spoonful of sugar is dissolving in hot water. The initial mass of the sugar was 7 grams
and 5 minutes later the mass present had halved. The mass of sugar, S grams, at time
t minutes after it was placed in the hot water can be modelled by S(t) = S0e−kt, t ≥ 0.
a State the value of S0.
b Find the exact value of k.
c Sketch the graph of S(t).
d To the nearest second, how long after the sugar was
placed in the hot water was its mass 1 gram?

how do i graph part c on my calculator, which equation do i use to graph it?

2. Mar 22, 2006

### Jeff Ford

The problem doesn't ask you to use your calculator, it asks you to sketch the graph. Find the values of S0 and k, as per parts a and b. Then substitute those values into the given equation for S(t) and sketch from there.

3. Mar 22, 2006

### HallsofIvy

The problem asks you to graph S(t)= S0e-kt Why would you have to ask "which equation do I use to graph it"?
Of course, you use the values of S0 and k you found in parts a and b.

Or are you asking how to enter it into the calculatorf?

Last edited by a moderator: Mar 23, 2006