View Full Version : 6th grade math help
My buddy sent me this math problem from his daughter's math class.
https://i.imgur.com/mvq9tAA.jpg
Her answer was wrong. He checked it and got the same answer. I did it and got the same answer.
What is the right answer?
We don't know yet. He's going to ask the teacher to show him the right answer next week.
I hope I don't have to ban anybody for this.
6th grade, not 8th.
crosseyedshooter
02-14-21, 13:39
I dunno, but I can’t get any of the answers!
Using the equation provided, Watts = Joules / seconds.
So, Watts x seconds = Joules.
= Watts x (30 days x 24 hours x 3600 seconds)
= Watts x 2,592,000
= (100W x 2,592,000) - (60W x 2,592,000)
= 103,680,000 J
Thanks. We all got the same answer. Glad to know. What did we miss? or were they wrong? I left out our answers in my first post so that I wouldn't lead you on.
crosseyedshooter
02-14-21, 14:08
The only variable assumption is “during this time.” If you back calculate the answers for the 40W difference,
A. 1 second
B. 30 seconds
C. 45 seconds
D. 75 seconds
That's a trick question. We assumed they referred to the whole 30 days, 24 hours a day, etc.
My buddy sent me this math problem from his daughter's math class.
https://i.imgur.com/mvq9tAA.jpg
Her answer was wrong. He checked it and got the same answer. I did it and got the same answer.
What is the right answer?
We don't know yet. He's going to ask the teacher to show him the right answer next week.
I hope I don't have to ban anybody for this.
6th grade, not 8th.
Yep I get 103,680,000 as well.
It's gotta be worded wrong or assuming 60 and 100 watts per day. Which is 1200J difference.
I use Wolfram Alpha. https://www.wolframalpha.com/
1_click_off
02-14-21, 15:27
I assume they are looking for A 40. This is just the difference in the bulbs during the timeframe and not the power consumed.
Looks like the person forming the question is not the same one providing the answers for the homework questions when the text book was printed. I have found many questions with answers like this in my kid’s books. It has gotten so bad the teachers will even write on the black board what the correct answers are to some of the questions so they will scan correctly due to the question not having a valid answer available. We have given up on the magnet program and went private.
I’m neither a technician nor a mathematician, but I got an answer of 1200J (B) taking too long to figure it out in my head.
Now I want to know...
BangBang77
02-14-21, 16:16
Watts is a UOM for Power. Joules/second is a UOM for Power. Both are interchangeable in the electrical world (1W = 1J/s AND 1Ws = 1J). Joule is a UOM for energy.
If 1W = 1J/s, and 100W - 60W = 40W, then 40W = 40J/s. As Joule is the UOM for energy and the question is asking for the answer in energy, we have to isolate the quantity of Joules by multiplying by the denominator, so 40W x s = 40J.
You only need to account for time if you're solving for power.
EDIT - A very poorly worded question, especially for a 6th grader.
Instead of teaching them debt to income ratios, proper credit utilization, personal finances, proper saving principles, and other useful life math skills, they're pushing the green agenda on them with lightbulb questions that the curriculum developer is incapable of understanding, hence the whole problem with the green agenda.
Adrenaline_6
02-14-21, 16:18
Yea, textbooks are wrong sometimes and many times, the teachers are too lazy to check it, even when the overwhelming answers should bring it into question.
They look at the the textbook answer key and move on.
I assume they are looking for A 40. This is just the difference in the bulbs during the timeframe and not the power consumed.
Looks like the person forming the question is not the same one providing the answers for the homework questions when the text book was printed. I have found many questions with answers like this in my kid’s books. It has gotten so bad the teachers will even write on the black board what the correct answers are to some of the questions so they will scan correctly due to the question not having a valid answer available. We have given up on the magnet program and went private.
I would agree with you. Of the four choices, 40 is the difference in power consumption. It is a poorly written question or tricky one.
Oh, btw, this is a private school, supposedly one of the most elite in the state.
, they're pushing the green agenda ........, hence the whole problem with the green agenda.
If they want to conserve energy, they need to ditch the 40 and 100w incandescent bulbs and use LED ! In new and renovated commercial buildings, only LED will meet the requirement of the Energy Code.
crosseyedshooter
02-14-21, 16:46
Watts is a UOM for Power. Joules/second is a UOM for Power. Both are interchangeable in the electrical world (1W = 1J/s AND 1Ws = 1J). Joule is a UOM for energy.
If 1W = 1J/s, and 100W - 60W = 40W, then 40W = 40J/s. As Joule is the UOM for energy and the question is asking for the answer in energy, we have to isolate the quantity of Joules by multiplying by the denominator, so 40W x s = 40J.
You only need to account for time if you're solving for power.
Your explanation makes sense to me. In other words solving for the difference in amount of energy transferred:
Power = Energy transferred (J) / time (s)
(100W - 60W) x time (s) = Energy transferred (J)
40W-s = Energy transferred (J)
Basically, the tense in transferred implies total energy over total time, but the question is asking for energy per unit time. If I reread the question as, “What is the difference in the amount of energy transfer...” it changes the whole question in my mind.
1200 is the answer they wanted
1_click_off
02-14-21, 16:52
Your explanation makes sense to me. In other words solving for the difference in amount of energy transferred:
Power = Energy transferred (J) / time (s)
(100W - 60W) x time (s) = Energy transferred (J)
40W-s = Energy transferred (J)
Basically, the tense in transferred implies total energy over total time, but the question is asking for energy per unit time.
I agree too. It was more of a word problem set up. That is why I chose A. 40J was the only answer that confirmed it was them simply wanting the difference in the bulbs, not energy consumed. I would have gotten it wrong had it not been multiple choice.
Wording of the Q is odd.
In for the answer!
crosseyedshooter
02-14-21, 17:19
Wording of the Q is odd.
In for the answer!
There’s the exact same question online except it’s 30 SECONDS. https://brainly.com/question/18188021
:suicide2::suicide2:
So many teachers are retarded and are hellbent on tricking the kids vs educating them with their insecurities and need to seem above the kids. We all can remember the great teachers and the little minded ones that beat us down. The latter sux cox.
PB
crosseyedshooter
02-15-21, 00:06
1200 is the answer they wanted
Then the question matching that answer should say "for 30 seconds..." instead of "30 days".
FromMyColdDeadHand
02-15-21, 01:07
I have a degree in chemistry, basically a minor in biology, and middle school 'science' teachers drive me nuts. They get way over their skis sometimes trying to be cute. Stick to the basics. When you fid that 1 in a thousand kid that you don't understand, stop talking to them and pass them off someone else that can get them to their full potential. Every teacher is looking to look good and innovative for parents night, when they need to be getting kids to understand the basics.
Case in point. A science teacher at our kids school is really proud of his project to get kids to plan and design their own animal. Kids come up with all these Chimera animals. I told my kids just take a coyote and copy it. Or a cockroach. You really think your suburban ass is going to either out design God or hundreds of millions of years of evolution? If the lesson ended with every kid failing, I'd think it was worth something. As it is, it is just an arts and crafts project.
That and they turned the science fair into a Shark Tank, well shallow end Shark Tank.
Then the question matching that answer should say "for 30 seconds..." instead of "30 days".
There are a lot of things wrong with wording of the question. The answers are also wrong. They should be in Wh not joules.
Q should ask for difference in power used and give a 1 day period. Then answers should be in Wh.
So many teachers are retarded and are hellbent on tricking the kids vs educating them with their insecurities and need to seem above the kids. We all can remember the great teachers and the little minded ones that beat us down. The latter sux cox.
PB
Hated that shit.
Had a word problem in Algebra and it was basically Johnny takes two cabs are two different rates and goes X miles for different values of time in cab with each cab and tell us what the total cost of the trip would be.
Well I did the exact math based upon the exact numbers and got it wrong because my teacher told me a cab would round up 1:45 to 2 hours so my answer wasn't correct. I told my teacher I'm in 8th grade and had never taken a cab in my life but was my math based upon my values correct (which I knew it was) and she wouldn't even take the time to check it because my answer wasn't in her teacher edition.
Never mind that I completely understood how to solve the math problem, because I wasn't taxi cab protocol educated I got it wrong.
MA2_Navy_Veteran
02-15-21, 09:33
Maybe it's just me, but it looks like the reason it was marked as wrong was because she circled the question, and not any of the answers?
StovePipe_Jammer
02-15-21, 09:38
After attempting this problem and getting wonky answers compared to what was listed, I enlisted the help of my wife (engineering PhD).
She got the same answers I did until she re-read the problem. She agreed it's incredibly poorly worded and they've got to be simply asking what the energy difference is between the two bulbs. It will only ever be 40J, whether it's 1 second or 30 days.
Going with answer A.
Anxiously awaiting the solution and explanation!
:D
Averageman
02-17-21, 09:22
Honestly, early on I had a Teacher that would sit you down and explain Math one on one if he needed to.
Now if you wanted that, you gave up a lunch or recess and he would work with you. In sixth grade I was deep in to Algebra one and staying ahead of the pack.
7th grade was a whole new ball game.
Grand58742
02-17-21, 13:41
It is a poorly written question or tricky one..
This. I'd have Daughter write in the correct answer, point out the major faults in the question and relay from Dad why the teacher can't do simple math before handing it back in.
FromMyColdDeadHand
02-17-21, 16:03
This. I'd have Daughter write in the correct answer, point out the major faults in the question and relay from Dad why the teacher can't do simple math before handing it back in.
The funny thing is the teachers used to be able to come back with “well why don’t you teach your kids then“. But with Covid we are teaching our kids.
Questions are often written in a "tricky" way as a means to make you think. They will hand you some irrelevant info that you need to figure out is not actually part of the problem. It is part of problem solving skills.
In this case, "poorly written" also seems to apply Since it specifically says "during this time" without specifying "this time", as the "30 days" does not seem to apply.
There are a lot of things wrong with wording of the question. The answers are also wrong. They should be in Wh not joules.
Q should ask for difference in power used and give a 1 day period. Then answers should be in Wh.
Questions are often written in a "tricky" way as a means to make you think. They will hand you some irrelevant info that you need to figure out is not actually part of the problem. It is part of problem solving skills.
In this case, "poorly written" also seems to apply Since it specifically says "during this time" without specifying "this time", as the "30 days" does not seem to apply.
^^^these
Wording stinks, j is almost always a snapshot of power, but I don't think whomever wrote the question knew enough to know that. A sixth grade student sure as heck ain't gonna know. I hope the teacher cares more than most or its gonna be "Answer key says..."
Unfortunately 6th grade is too early to start teaching the real point of this. Having the right answer does not always mean you win. No matter what I'm guessing we are way more wrapped up in this than your 6th grader.
This. I'd have Daughter write in the correct answer, point out the major faults in the question and relay from Dad why the teacher can't do simple math before handing it back in.
Yea that'll be gladly accepted! :D
Like arguing Constitutional law with a LEO during a traffic stop. Not gonna end how you imagine!
Test writer wanted 30s, but airballed with 30D (otherwise, 103.7MJ is the right answer).
If the teacher doesn't see that there's a verbal typo on that, then teacher needs to be set straight - but for your part as a parent, show how you can get to how the answer makes sense, and see what other questions your kid has, and make it actually fun to answer those
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.