6th grade math question

[Mickey'snewestfan]

I'm embarrassed that I'm asking this question because I'm a professional darn it, but I was stumped the other day by a sixth grade homework question.

Here's the question:

Mickey bought an electric drill for 91% of the regular price. He paid $26 for the drill. What was the original price?

Now, I can do this, of course,

26 = .91P

26/.91 = P

P = $28.57

Except that the kid I was tutoring goes to a school that teachers dividing by a decimal in the second half of sixth grade, and it's still first semester.

No problem, I can do it this way:

26/P = 91/100

26/P x 100 = 91/100 x 100

2600/P = 91

2600/P x P = 91 P

2600 = 91 P

2600/91 = P

P = $28.57

OK, great, but still no go because not only haven't they teach division by a decimal they haven't taught dividing by a 2 digit number.

So, am I missing some third way to solve this problem? If so, what? Every other problem on the page had numbers you could figure out without long division, but to me, solving this one without division was like working with one hand tied behind my back.

 

[meliss8599]

$26 x 0.91 = $23.66

 

[ColoradoDisneyFreaks]

never mind.

 

[sonnyjane]

You have a typo in your OP... the answers, no matter how you found them, should both be the same.

 

[Mickey'snewestfan]

$26 x 0.91 = $23.66

That would work if the drill originally cost $26, but it didn't $26 is what the cost was with the discount.

The other problems were like that above, in which case you could solve via multiplication, which has been taught, or they were like this:

Mickey bought an electric drill for 75% of the original price. He saved $5 on the price. What was the original price and how much did he spend?

So you could figure it out without a lot of calculation, just by knowing that 75% is 3/4 and doing something like this:

5 = 1/4 P

5 x 4 = P

Or even just kind of figuring it out intuitively.

 

[skatalite]

You lost me at 26 = .91P

Seriously, I'm going to be the most useless parent when it comes to math. English, science, history... Got that covered. BUT MATH?! No bueno.

 

[Mickey'snewestfan]

You have a typo in your OP... the answers, no matter how you found them, should both be the same.

Okay, this is weird. You're right (and I fixed the typo) but what you're quoted as saying is not what you said in your post. How did that happen?

Anyway 26 x 1.09 doesn't work because it's adding 9% of 26, which is slightly less than 9% of the original price. It will give you a ball park figure, but not on the dot.

26 x 1.1 would be closer, $28.60 (so 3 cents off), because 10% of 26 would be 9.1% of the original price, but the reasoning for that is still above a sixth grade level.

 

[Mickey'snewestfan]

You lost me at 26 = .91P

Seriously, I'm going to be the most useless parent when it comes to math. English, science, history... Got that covered. BUT MATH?! No bueno.

Which is fine, because you can just hire a well qualified experienced tutor like me!

I might just have to conclude that they forgot an f and they really meant to write that it was 91% OFF instead of OF because then you're just calculating with a 9 and he's covered that!

 

[sonnyjane]

Okay, this is weird. You're right (and I fixed the typo) but what you're quoted as saying is not what you said in your post. How did that happen?

Anyway 26 x 1.09 doesn't work because it's adding 9% of 26, which is slightly less than 9% of the original price. It will give you a ball park figure, but not on the dot.

26 x 1.1 would be closer, $28.60 (so 3 cents off), because 10% of 26 would be 9.1% of the original price, but the reasoning for that is still above a sixth grade level.

When I posted Colorado had a different answer above me. I think the bottom line is that we are all dumb ahahha! I know how to REALLY solve it. I'm bad at these "solve it using xyz methods" type questions.

 

[wgeo]

Ok sorry in advance if I'm not being helpful.

I just asked my 4th grader (he is in advanced math for his age) and read him the problem. He immediately said he would take 26 and divide it by .91 and came up with the answer (after writing it down and using pencil/paper). I believe that they are only doing math one grade ahead in his class, which means 5th grade and he was very comfortable with dividing by decimals- although it took him a second to actually do the work - so that is how he came up with the answer. Is there any chance that you might possibly be wrong about when they introduced dividing by decimals?

I'm trying to come up with another solution, but of course once you have an answer it's always harder to come with the same answer done in a different way - but if I think of something different I'll post again.

 

[StephMK]

My 5th graders were dividing decimals yesterday so it would be reasonable that they may know this skill in 6th.

DS is in Algebra and DH immediately hands off all math related questions to me. I'm about at my limit so DS will have to start calling his sister at college!

 

[LuvGoofy6]

f

 

[Mickey'snewestfan]

Don't you have the right answer? If the original price is the $28.57 (your answer) and then take 91% of that which is what he paid. 28.57 x .91 = 25.9987 or $26.00.

My answer is the right answer. But I'm a tutor, not a mathematician. So, my job isn't to find the right answer it's to ask the right questions or demonstrate in the right way so that the kid can find the right answer.

Without stopping and doing a unit on two digit divisors, which I shouldn't have had to do given that they haven't taught it yet.

I guess it's possible that they taught it last year, although this kid wasn't at this school in 5th, but two digit divisors haven't appeared in a single worksheet, including all of the basic computation review they did in the fall. If they did teach it, I would have expected it to be reviewed when they reviewed 1 digit divisors and mutlidigit multiplication.

 

[Jennasis]

I reject the question. No store sells things for 91% off.

 

[snarlingcoyote]

This would be a painful way to do it, but, conceivably, you could do this:

Price Sold(PS) = 26
Original Price = x
Percentage of PS paid = .91

And then take a stab at x in the dark.

91 is most of 26, but not all, so the number must be close to it.

So first try 27 as x. 27*.91=24.57. Too low. Way too low.
So try 29 as x. 29*.91 = 26.39 Too high, but not by much!

We now know it's between 27 and 29 and probably close to 29 than 27.

Hmmm.

Maybe 28? 28*.91 = 25.48.

Hey, that's fairly close!

Let's try 28.5! 28.5*.91 = 25.94 (rounded). Very, very close, just a few cents off.

28.55*.91 =25.98. So hot we can feel the answer now!

28.57*.91 = 26! You got it.


That's the only thing I can think of, because when I taught HS (English) I would tutor some kids in math and I've actually seen some of them stumble through questions in EXACTLY this manner; I'm sure OP has seen worse!

 

[marlynnp]

I reject the question. No store sells things for 91% off.

It was 9% OFF -- 91% of the regular price


I don't know what to tell you in regards to them not having been taught division yet really?

but the answer is

(26/91)*100 = 28.57

 

[rickybobby]

I stopped learning math after I managed to master gazinta math.

 

[rickybobby]

4 gazinta 20 5 times.
8 gazinta 64 8 times.

Disclaimer: The above was stolen from an episode of The Beverly Hillbillies.

 

[kimmar067]

I'm embarrassed that I'm asking this question because I'm a professional darn it, but I was stumped the other day by a sixth grade homework question.

Here's the question:

Mickey bought an electric drill for 91% of the regular price. He paid $26 for the drill. What was the original price?

Now, I can do this, of course,

26 = .91P

26/.91 = P

P = $28.57

Except that the kid I was tutoring goes to a school that teachers dividing by a decimal in the second half of sixth grade, and it's still first semester.

No problem, I can do it this way:

26/P = 91/100

26/P x 100 = 91/100 x 100

2600/P = 91

2600/P x P = 91 P

2600 = 91 P

2600/91 = P

P = $28.57

OK, great, but still no go because not only haven't they teach division by a decimal they haven't taught dividing by a 2 digit number.

So, am I missing some third way to solve this problem? If so, what? Every other problem on the page had numbers you could figure out without long division, but to me, solving this one without division was like working with one hand tied behind my back.

....yeah....a. calculator.

 

[kimmar067]