<p>I was shopping in a department store today. I was going to a sales rack where there was 40% off. I over heard two young girls asking each other how much something was after the discount. The conversation went on for a few minutes. I turned around and asked, “How much is on the tag?” At that point, I noticed one of them had a calculator and they looked like they were in high school. One girl said, “It’ $117.” I round it up to $120, and I said, “It would be around $72.” I continued to shop. Then they said, “We have a coupon for 20% off, what would it be with another 20% off.” I said, “Just take another $14 off, so around $55.” It occurred to me that even with a calculator they didn’t really know how to apply various discounts. </p>
<p>I know most kids on CC are probably the top 5-20% of high school population, but it is scary to me that there are kids out there who don’t even know enough math to operate day-to-day. Maybe we should worry less about AP courses, but have more practical courses to teach our young people how to run a household budget, mortgage calculation, interest earned (paid).</p>
<p>The problem is that our school districts have all been pressured on the state and federal level to teach kids how to be test responsive on standardized assessment tests that are tied into funding for the schools. Curricula have been altered and classroom time redirected to achieve scores. Instead of “No Child Left Behind”, we have “No Child Taught to Think”.</p>
<p>I used to work with a former CS professor at a third-tier. He was teaching a intro course and there were math majors in his course so he assumed that they were familiar with logarithms.</p>
<p>It turned out to be a bad assumption so he had to do a mini-refresher on logarithms. If math majors in college can’t do logarithms, imagine how those outside of STEM are doing. Well, you don’t have to imagine it, you can see it at Kohls.</p>
<p>Regarding practical course. D2 wants to take a course in automotive technology. She wants to be able to know what’s wrong with her car and at least learn how to fix some basic stuff. I think she turned out to be the son my husband wished he had so he can do car talk. :D</p>
<p>I teach 2nd through 5th grades in math, and I’m amazed at how poorly math books cover the basics. They never truly help youngsters understand how the number system works, yet it is so simple! (and I was an art major in college.) For some reason, the curriculums are all so focused on teaching partial numbers as fractions, yet even the stock market switched away from fractions years ago. I constantly show my students the decimal forms of common fractions, although the math books barely cover that. I learned those basics when I worked at a fabric store throughout HS and whoa, how helpful! I say do away with all that computations of fractions and use decimals. Much more practical.</p>
<p>I find it much easier to start with the percentage that one pays. For example, if something that costs $120 is 20% off, it is easier to see that what you pay is 80% of $120. I would multiple $120 by 8 and get $96. It is much easier than figuring the 20% discount and then subtract from $120.</p>
<p>I was in CVS yesterday and saw Halloween decorations were 90% off. As I was crowding around the table, a few adults could not figure out what the final sale prices were. I told them to just move the decimal pt (of the list price) one place to the left.
Students should be taught these shortcuts.</p>
<p>My dad helped me a lot with mental math as I was growing up (and I wasn’t good at math, which is why he did it, I guess).</p>
<p>It’s easy to figure out percentages off in a sale in your head. Just think of 10% and go from there. For example, for the 40% off $120, think of what 10% off would be–$12. So 40% off would be 4 X 12 + $48. Subtract that from $120 = $72. </p>
<p>My dad also taught me to round numbers up or down when making mental calculations like this, since I wasn’t too good at adding and subtracting mentally. So if I need to subtract 48 from 120, I would first round that 48 up to 50, subtract from 120, and then subtract the extra 2.</p>
<p>So if you needed to find 20% of $72, you find 10% of $72, $7.20. Double that to get the 20% = $14.40. If I had to subtract that in my head, I would take away $10 from $72 (=$60), then $4 (=$58), then the .40 (=$57.60).</p>
<p>90% is easy. You just figure out what 10% is, and that is the price.</p>
<p>Trust me, if my girls needed to figure out 20% off the price of a coveted bag or sweater, they would easily do so without a calculator, but they would not hesitate about whipping out their TI-whatever to solve a similar math problem not involving clothes :D</p>
You would just take 10% of the number twice. So $7.20 plus 7.20 equals $14.40</p>
<p>I don’t think we can blame schools for this. I think it’s partly a matter of some things being easier for some people than others and secondly a matter of confidence. My sister is a doctor. I couldn’t pass Biology if you paid me, but when shopping together, she asks me how much she’d have to pay for an item that is 40% off plus a 20% off coupon. I’ve tried explaning the tricks to her, but she just doesn’t trust herself to get it right.</p>
<p>When I was working as a volunteer at a school book sale, one of the women who was on the school board was adding the prices up on a piece of paper, then figuring the 6% sales tax and then adding it to the total. I told her to take the total and multiply by 1.06 and she’s save a step. She asked me how that worked.</p>
<p>There is a compounding effect of which order you apply the discount(applying 40% first then 20% next has a different effect than 20% first then 40%), but even just applying 60% off $120 (north or $48) would give those young kids a good approximation.</p>
<p>I think if we were teach math in such a way that kids could relate to - discount on clothes, cars; applying sales tax on purchase; income tax calculation (different bracket)… - our kids may show more interest, and could actually become more functional human beings.</p>
<p>There was a Foxtrot strip not too long ago where Paige couldn’t make sense of an algebra problem using x’s and y’s, but when her brother changed the problem to be about shirts and skirts she had no problem. :)</p>
<p>I think it’s easier to find 80% of the full price than it is to calculate the 20% discount - and I usually figure out 10 percent and then multiply it by the first digit.</p>
<p>oldfort, there was a program called “Everyday Math” that my school district incorporated into the curriculum for elementary school kids and it was a disaster. They got into junior high relying too heavily on calculators, not understanding the relationships in math processes, couldn’t do math the “long way” on paper and couldn’t do basic percentages, division and other arithmetic functions in their heads. It didn’t even make them better shoppers ;).</p>
<p>One thing that bugs me is when something is, say, $14.96 and I give them $15.01, and they seemed stumped that I’d rather have a nickel back than four pennies.</p>
<p>I learned how to give change back in the early 70’s when working in my uncle’s convenience store when the cash register didn’t calculate the change for you. Nowadays, all calculations are done by machines and we just don’t need to think.</p>
<p>My son and I were having this discussion last evening. Kids in his class asked him why they don’t teach classes on how to balance a checkbook, figure out discounts and just general life lessons we no longer teach.</p>
<p>In D’s Math Studies class the students had to pick a house listed on MLS that they liked, and then calculate how much income they had to have (and what kind of jobs could provide this income), what downpayment they had to make, etc. to be able to afford the mortgage and property taxes on this house. It was not exaclty a higher level math problem, buy it was an eye opener for many kids.</p>
<p>I bought something today that came to $6.93. I gave the cashier a ten dollar bill and ninety three cents. She must have rung up just the bill because the register said the change should be $3.07. I told her that was wrong. She could NOT figure out what it should be. I had to explain it very carefully. That’s the problem with relying on machines.</p>