5th grade math help please!!!

[Lisa L from MI]

This is driving me nuts....I know there is a simple way to figure this out....but I can't...neither can DH!!!!

If it takes 1 hour and 40 minutes to go 80 miles.....how fast are you going????? I know there should be some simple formula to figure this out.....anybody know?? We figured out the first one quick which was it took 1 hour to go 80 miles....


Thanks in advance!!

 

[JetMom]

80/100 = X/60


It's a ratio. If you go 80 miles in 100 minutes, how many miles would that be in 60 minutes. X= miles in 1 hour.

 

[cruisnfamily]

Well, that's 100 minutes to go 80 miles.

That's 1.6667 hours

Divide 80 miles by 1.6667 hours = approx 48 miles per hour

Does that sound right???? It's the best I can do off the top of my head but it doesn't sound right for 5th grade math...too complex.

Am I even correct?

 

[cruisnfamily]

Well, that's 100 minutes to go 80 miles.

That's 1.6667 hours

Divide 80 miles by 1.6667 hours = approx 48 miles per hour

Does that sound right???? It's the best I can do off the top of my head but it doesn't sound right for 5th grade math...too complex. My daughter is in 5th grade and could do a similar problem if it worked out to round numbers....I can't imagine the division with decimals though.

Am I even correct?

What was the first problem....are you sure you got that right?

 

[elgerber]

I'm not sure if this is right, but I took the 80 miles, divided by the 100 minutes, to get .80 miles per minute, then multiplied by 60 minutes in an hour to get 48 mile per hour.

Anyone else get that answer? My 5th grader is too busy snacking to help.

Erika

 

[JetMom]

Cruisinfamily -- you got the right answer, you just did it the hard way! If you do it as a ratio, it is whole numbers.

 

[Lisa L from MI]

I kinda got 48 too.....i thought too, that 5th grade math shouldn't be that complex either....but they did say an "average"......so I guess 48 would be right.

The first question was it took 1 hour to go 80 miles....so that was 80 mph...........I guess sometimes you think too much into it...


THANKS all!!!!!!

 

[JetMom]

80/100 = x/60

100x = 4800

100x/100 = 4800/100

x = 48

You are traveling at 48 m.p.h.

 

[cruisnfamily]

Originally posted by JetMom
80/100 = x/60

100x = 4800

100x/100 = 4800/100

x = 48

You are traveling at 48 m.p.h.

Boy now I feel dumb!

When you post it that way it's really simple and DD could do the math.

What she couldn't do is figure out that method...she would never think of 80/100=x/60 . That's algebraic thinking and she would never arrive there on her own. If I gave her that equation though she would keep reducing the fractions and then multiply it out.

I still think it's beyond the average 5th grader....was this for extra credit or some kind of "problem solving" thing? Doesn't sound like the regular curriculum.

 

[Lisa L from MI]

I did it on paper too that way....that was what I was trying to figure out from the get go (I love algebra...so it kinda brought back memories).

This was her everyday work...I just think it is more of learning to "estimate" etc....they do that chicago math or everyday math (something like that) that I have NO idea what she is doing.......things with lattices etc......so even simple problems I am really no help!!!

They don't even have a math book either. The teacher explains in school and they take just sheets home......so I told her to pay more attention and ASK questions if she doesn't understand.......

 

[Shel]

Look! Over here! Someone who can't do 5th grade math!!! I hated math/algebra in school and even flunked a 6 weeks!
When God was passing out math brains I must've been in the bathroom!!!!!

 

[peg2001]

I don't think this problem is beyond 5th graders. There are several ways to look at it. Here's one that doesn't require algaebra:

speed = miles per hour = miles/hour

Given the distance of 80 miles and the time of 1 hour and 40 minutes, it is simply a fractions and division problem. How many hours is 1 hour 40 minutes? Then, what is 80 miles/1.67 hrs? (I'll admit to wanting a calculator for the last part!)

Peggy

 

[cruisnfamily]

Originally posted by peg2001
I don't think this problem is beyond 5th graders. There are several ways to look at it. Here's one that doesn't require algaebra:

speed = miles per hour = miles/hour

Given the distance of 80 miles and the time of 1 hour and 40 minutes, it is simply a fractions and division problem. How many hours is 1 hour 40 minutes? Then, what is 80 miles/1.67 hrs? (I'll admit to wanting a calculator for the last part!)

Peggy

I agree, I believe my daughter would have pursued it exactly this way. The thing that threw me is the division with decimals....they're just not doing that....they still use remainders(at least in our school)...so I can't imagine them being required to do it this way. The algebra way makes alot more sense but I don't see how they would come up with the equation on their own.

 

[peg2001]

Originally posted by cruisnfamily
I agree, I believe my daughter would have pursued it exactly this way. The thing that threw me is the division with decimals....they're just not doing that....they still use remainders(at least in our school)...so I can't imagine them being required to do it this way. The algebra way makes alot more sense but I don't see how they would come up with the equation on their own.

Oh! I see what you are saying now. Are they, by any chance, allowed to use calculators? That would make it simple enough.

Peggy

 

[cruisnfamily]

Originally posted by peg2001
Oh! I see what you are saying now. Are they, by any chance, allowed to use calculators? That would make it simple enough.

Peggy

They're not allowed to use calculators at my DD's school. I don't know about the OP's. Sounds like quite a challenging curriculum they're pursuing over there.

I'm very, very pleased with the academics at DD's school but it's a "fundamental" or "magnet" school with a "back to basics" kind of philosophy and they dont' pursue the problem solving things very much there.(DD is very weak in problem solving...she can do the work once you tell her what to do but she has trouble figuring out what to do on her own.)

 

[peg2001]

Originally posted by cruisnfamily
I'm very, very pleased with the academics at DD's school but it's a "fundamental" or "magnet" school with a "back to basics" kind of philosophy and they dont' pursue the problem solving things very much there.(DD is very weak in problem solving...she can do the work once you tell her what to do but she has trouble figuring out what to do on her own.)

Basics are critical, as you know. However, I think it is important for people to learn how to problem solve as well. Have you seen the series of books called "Building Thinking Skills"? I picked one up used and am looking forward to working through it with my DDs. It looks like fun!

Peggy

 

[KarenC]

Originally posted by Lisa L from MI
they do that chicago math or everyday math (something like that) that I have NO idea what she is doing.......things with lattices etc......so even simple problems I am really no help!!!

My kids had the University of Chicago Everyday Mathematics program. When they were young, I really thought it was terrible. How could they be proficient in Math if they didn't memorize the "times tables"? My fears were unwarranted.

My daughter just graduated from high school and has an incredible grasp of math concepts. She took a little multi variable calculus and linear algebra while still in high school. Now that she's in college she's finding herself two or more years ahead of her peers in math. (And way ahead of her mother!) She received an A in her Calc 2 for engineers class in college.

The exercise your fifth grader did last night is building the groundwork for her to be able to grasp higher level math concepts sooner rather than later. It's good to provide our kids with that capability since most of the "good jobs" in their future will depend on having a strong grasp of mathematics.

It took a leap of faith in our highly regarded school district for me not to go crazy over that U of C math program. But having seen it to the end, I think they do know what they're doing.

 

[damo]

I don't think that in fifth grade they know how to cross multiply or even solve equations, at least they don't with our curriculum. I don't think that ratio is taught for a few years yet. The question is probably more of a simple division question, given that the formula for speed is distance divided by time.