``````public static void main(String[] args){

/*The number of bacteria, B, in a culture that’s subject to refrigeration can be
approximated by this formula:
B=300000*e^-0.032t
Using this formula, write a program that prompts the user for a value of time, calculates the
number of bacteria in the culture, and displays the result. */

Scanner i=new Scanner(System.in);
double B,e=2.71828,t;
Math.pow((double)e, (double)t);

System.out.println("Please input your value of time: ");
t=i.nextDouble();

** B = (300000)*Math.pow(e),(-0.032 * t);**
System.out.println("Number of bacteria: "+B);

}

it gives me an error
how can i make a formula multiply with that e^-0.032t?
``````

The easiest way to get (e to the power something) is to use `Math.exp(something)`, eg

``````eToThePowerFour = Math.exp(2*2);
``````

## All 4 Replies

The easiest way to get (e to the power something) is to use `Math.exp(something)`, eg

``````eToThePowerFour = Math.exp(2*2);
``````
``````Scanner i=new Scanner(System.in);
double B,e=2.71828,t;
**e=Math.exp(-0.032*t);**

System.out.println("Please input your value of time: ");
t=i.nextDouble();

** B = (300000)*e;**
System.out.println("Number of bacteria: "+B);
``````

Quoted Text Here

can i declare the value of e at the top so that my formula will give me this B = (300000)*e;?

Well, you can if you want. That is valid Java, but it doesn't match the formula you were given. Exponentiation comes before multiplication, so its
B=300000(e^-0.032t)
not
B=(300000
e)^-0.032t

ps You;ll get a more accurate result by using the built in value for e, which you can access as just
Math.E

ok sir thanks! :)

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