# stupid math problem!!!

Discussion in 'General Education' started by Learner4Life, Jan 24, 2011.

1. ### Learner4LifeCohort

Joined:
Sep 19, 2007
Messages:
720
0

Jan 24, 2011

I really really really wish that the text books would tell you how they got the answer to the questions!!!! ESPECIALLY the story problems. I've given one of the problems for extra credit two years in a row now because I have NO idea how they got the answer!!! No one has been able to come up with an answer!!!

Joined:
Jun 21, 2007
Messages:
490
12

Jan 24, 2011

Don't keep me in suspense. What is the problem!

4. ### Learner4LifeCohort

Joined:
Sep 19, 2007
Messages:
720
0

Jan 24, 2011

I was going to post it on here because I knew someone would be able to give it to me, but there's a chart involved... I'll have to think about how to post it.

5. ### moparMultitudinous

Joined:
Aug 15, 2010
Messages:
10,924
0

Jan 24, 2011

Many textbooks now do have a solving guide with the textbook.

I would definitely post the question....just describe the chart if need be.

Joined:
Apr 7, 2005
Messages:
3,231
66

Jan 24, 2011

can you scan or take a picture of the chart?

7. ### Joyful!Habitué

Joined:
May 5, 2009
Messages:
881
211

Jan 25, 2011

The suspense is killing me!!!!!!!!!!!!!!!!!!!!

8. ### PeachynessVirtuoso

Joined:
Jul 14, 2006
Messages:
6,181
1

Jan 25, 2011

Yeah, that's just not fair! PLEASE!! Post it!!!!

9. ### Learner4LifeCohort

Joined:
Sep 19, 2007
Messages:
720
0

Jan 27, 2011

Okay here it is: (sorry it took me so long)

George exchanged some U.S. currency for 23.568 in European Euros. Then he traded the euros for 233.736 in Hong Kong dollars. How much did George exchange in U.S. dollars?
The exchange rate they put in the book is 5 U.S. dollars for every 3.928 euros and 15 U.S. dollars for every 116.868 Hong Kong dollars.

They say the answer is 30.

10. ### Catcherman22Companion

Joined:
Feb 20, 2007
Messages:
152
0

Jan 27, 2011

set up a ratio...

x/23.568 = 5/3.928

3.928x = 117.84

solve for x by cross multiplying

the bit about trading it for another currency is extra info that's not needed for the problem

11. ### Learner4LifeCohort

Joined:
Sep 19, 2007
Messages:
720
0

Jan 27, 2011

Okay so obviously, I'm not a Math person... but my 5th graders were supposed to figure that out?!?!?! Can you explain it without cross multiplication?

12. ### moparMultitudinous

Joined:
Aug 15, 2010
Messages:
10,924
0

Jan 27, 2011

The students could make a table. Start with a column for US and a column for euros. Then put 5 under US and 3.928 under euros. Then add 5 to the US side and 3.928 on the euro side until they get to 23.568 on the euro side. Whatever is on the US side is the answer (it should be 30).

13. ### HMMCohort

Joined:
Dec 21, 2004
Messages:
694
1

Jan 27, 2011

233.736 HKD*(15 US/116.868 HKD)=30 US

14. ### 123456nowRookie

Joined:
Jan 16, 2009
Messages:
90
0

Jan 27, 2011

Another way to solve would be:

Find how many euros for \$1 by dividing 3.928 by 5. Then, you see that \$1=0.7856 euros. Then, divide 23.568 by 0.7856 to see how many dollars that would be. 23.568/0.7856=30.

15. ### SargeEnthusiast

Joined:
Jan 13, 2007
Messages:
2,483
205

Jan 27, 2011

The Hong Kong dollars have nothing to do with the problem. That's part of it.

(5/3.928)x23.568=30

Joined:
Apr 7, 2005
Messages:
3,231
66

Jan 27, 2011

For grade five, I would probably go with mopar's solution, although 123456now's answer may also work, depending on what skills they have... I haven't taught fifth grade Math apart from working in Resource, and supporting a class... and that was quite some time ago... so I don't remember what comes when.

I think the table might be your best bet.

17. ### moparMultitudinous

Joined:
Aug 15, 2010
Messages:
10,924
0

Jan 27, 2011

It really depends on if you let them use a calculator or not....

Joined:
Nov 22, 2009
Messages:
3,094
0

Jan 27, 2011

I agree with using the table. I teach 6th grade math and LOVE to give my kiddos challenging questions, but I would probably skip this one because I think the division might be a bit complicated. They know how to do long division, but the extended decimal portion would be very confusing for them.

If I DID give this question, it would be for extra credit only or as a group exercise and I would absolutely let them use a calculator.

19. ### SargeEnthusiast

Joined:
Jan 13, 2007
Messages:
2,483
205

Jan 28, 2011

In the Air Force, my job was to take a 148,000 lb airplane, loaded with up to 60,000 of cargo and up to 125,000 lbs of fuel and figure out the center of balance within 1/10 of an inch.

The arithmetic required was not as difficult as the word problem we are looking at.

20. ### AliceaccMultitudinous

Joined:
Apr 12, 2006
Messages:
27,534
6

Jan 28, 2011

Why not just teach them to cross multiply? It's an easy concept, the mechanics are very visual, and it's a skill they'll need in the future anyway.

Joined:
Dec 21, 2004
Messages:
694