A few days ago, I posted a YouTube video which posed a very basic problem relating to an investment. The purpose was to get people to revisit some very basic algebra. Over time, most of us have started relying heavily on calculators and computers and have often shown tendencies towards loosing these basic mathematical skills.
In all there were 6 unique comments and all had the right answer. However, the time taken to solve the problem varied between 10 seconds (?) and 8 minutes. The people who gave correct answers are: Tom, Pete, Keith and Teri, Jon, and Dimes. I would like to assume that Trent had the right answer but did not post it. Thanks guys for participating.
Now the solution (by one possible easy method)
Essentially, the problem statement was: A person invests a total of $7200. Part of that is invested at 4% annual rate of return and the rest of it at 5% return. If the return from each investment is the same, find the income from each investment.
Let the amount invested at 4% be P; the remaining amount = (7200 - P) is invested at 5%
The return on 4% investment = P *4/100;
The return on 5% investment = (7200-P) * 5/100;
Since these returns are equal, our equation is:
==> 9*P = 5 * 7200
==> P = (5 * 7200)/9
Now, 72 is directly divisible by 9 ( 9 * 8 = 72 ), so no need for a calculator here. After dividing by 9, we have:
Now, the return on this P at 4% = 4000 * 4/100 = 160;
the return on the remaining amount at 5% = 3200 * 5/100 = 160.
This is your final answer.
You could do this in many different ways and equally simpler ways. I would really love it if people do this without using calculator/excel solvers. Solve some simple problems once in a while to stay in good algebraic-shape.
{ 1 trackback }
{ 5 comments… read them below or add one }
I definetly did not solve this problem this way. I feel like lesser man right about now because I would have never figured it out using that method! I did like the challenge.
Jon: math does not make us lesser or greater
so don’t worry about this problem much. It’s just a matter or being in touch with algebra.
I used x instead of P and formed my equation thusly (same thing, but backwards):
.05x = (7200-x).04
.05x = 288-.04x
.09x = 288
x = 3200
then plug x into original equation and solve.
I agree calculators are too widespread and at a very early age. Around here there are a lot of kids in 4th and 5th grade who only know how to multiply on the calculator and do not understand their basic times tables. This is a very serious problem, but apparently it’s too much work to learn your times tables nowadays.
Dimes: Seriously, when I was a kid, we were made to learn multiplication tables till 30! …and now I have forgotten atleast 10 of them (the last 10).
ang galing tlaga nla
kyang-kya nlang ma-i-ans.ang
question i hope mas ma-
rami pa me maintindihan!!!!!!
Leave a Comment