Don't know what equation to use

[someonesomewhere]

Hi!

I'm stuck on the following question. It looks very easy, I just don't know what equation to use:

If a person who weighs 200kg loses 3% every month, how long will it take to reach 80kg?

Thank you!!

 

[someonesomewhere]

Ps -

I'm very sorry if this is in the wrong category, I wasn't sure.

 

[JeffM]

Hi!

I'm stuck on the following question. It looks very easy, I just don't know what equation to use:

If a person who weighs 200kg loses 3% every month, how long will it take to reach 80kg?

Thank you!!

ALWAYS start by assigning unique symbols to your variables.

\(\displaystyle Let\ n = number\ of\ months,\ where\ n \in \mathbb I\ and\ > 0.\)

\(\displaystyle Let\ w_n = weight\ at\ end\ of\ month\ n.\)

\(\displaystyle And\ 200 = weight\ at\ start\ of\ month\ 1.\)

If you do not see a general equation, you can always try some simple examples.

\(\displaystyle w_1 = 200(1 - 0.03) = 200 * 0.97^1.\)

\(\displaystyle w_2 = (200 * 97^1) * 0.97 = 200 * 0.97^2.\)

\(\displaystyle w_3 = 200 * 0.97^2) * 0.97 = 200 * 097^3.\)

Now let's generalize

\(\displaystyle w_{n} = 200 * 0.97^n.\)

Do you see how to do your problem now?

 

[someonesomewhere]

Hi JeffM,

Thank you very much for answering my question. I actually got some help from someone sooner but I do appreciate it.

ss

ALWAYS start by assigning unique symbols to your variables.

\(\displaystyle Let\ n = number\ of\ months,\ where\ n \in \mathbb I\ and\ > 0.\)

\(\displaystyle Let\ w_n = weight\ at\ end\ of\ month\ n.\)

\(\displaystyle And\ 200 = weight\ at\ start\ of\ month\ 1.\)

If you do not see a general equation, you can always try some simple examples.

\(\displaystyle w_1 = 200(1 - 0.03) = 200 * 0.97^1.\)

\(\displaystyle w_2 = (200 * 97^1) * 0.97 = 200 * 0.97^2.\)

\(\displaystyle w_3 = 200 * 0.97^2) * 0.97 = 200 * 097^3.\)

Now let's generalize

\(\displaystyle w_{n} = 200 * 0.97^n.\)

Do you see how to do your problem now?