# Exponential decay problem

#### DeusAbscondus

##### Active member
Hi folks could someone please check my calculations contained in attached file?
thanks.

(incidentally, how can i create a link to such files in the future, weaving them into my text?)

Deus(has gone)

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#### Bacterius

##### Well-known member
MHB Math Helper
Re: exponential decay problem

[JUSTIFY]Yes, it is correct, if $t$ represents hours (it is not made clear in the problem what the unit of $t$ is). For instance, if $t$ was in minutes, then you need to substitute $t = 4 \times 60 = 240$. I think it is meant to be hours though.

Be careful what each symbol means. For instance, in the first question, it says "500kg of raw sugar has been refined to 380kg". Does that mean that there is 380kg of raw sugar remaining, and that there is 500 - 380 = 120kg of refined sugar, or the opposite? Or something else? (sorry, I am not familiar with sugar refining) This will affect the meaning of (and answers to) the questions.

In word problems the hardest part is often (at least to me) understanding what the problem is and converting it to math. They often have little traps built-in to confuse people and make them pay attention to wording, it can be frustrating actually.[/JUSTIFY]

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#### DeusAbscondus

##### Active member
Re: exponential decay problem

Thanks Bacterius,
Worked out where I was reading the question wrong.
But it helped - as always - to have another set of eyes look at my work.

Cheers mate,
D'Abs

[JUSTIFY]Yes, it is correct, if $t$ represents hours (it is not made clear in the problem what the unit of $t$ is). For instance, if $t$ was in minutes, then you need to substitute $t = 4 \times 60 = 240$. I think it is meant to be hours though.

Be careful what each symbol means. For instance, in the first question, it says "500kg of raw sugar has been refined to 380kg". Does that mean that there is 380kg of raw sugar remaining, and that there is 500 - 380 = 120kg of refined sugar, or the opposite? Or something else? (sorry, I am not familiar with sugar refining) This will affect the meaning of (and answers to) the questions.

In word problems the hardest part is often (at least to me) understanding what the problem is and converting it to math. They often have little traps built-in to confuse people and make them pay attention to wording, it can be frustrating actually.[/JUSTIFY]