A mathematics problem

[Craig66]

I have a 6th grade math problem that I am in disagreement with the teacher with and would like the input of the people that know the most - Divers

Two guys decide to seperate their property by plaing a fence along the property line. They ordered enough posts so that the fence would have posts placed 8 feet apart but when the posts arrived 5 were not usable. They were still able to put the fence up by placing the remaining posts 10 feet apart.

How many posts did they originally order

Thanks guys and gals

Craig

 

[redacted]

(x-1)8=(x-6)10

x=26

Don't forget the end post. X is the nyumber of posts. (X-1) is the number of 8 ft segments. It is 200 ft of fenceline.

 

[dmoore19]

Math is hard.

 

[SC_Hoaty]

The answer is......................25

20 * 10=200
25*8=200

Draw it as a picture, and you will discover you have forgotten one end post. 26 posts at 8 feet apart, 21 at 10 feet.

 

[dmoore19]

Damn, I caught my mistake after I posted.

 

[Craig66]

Guys thanks - agree 100% with the awnser of 26 but when the math teacher told my daughter it was 25 I figured if I am wrong I can never go on a dive again as all the tennants of my nitrox and pressure calculations would fall flat.

Craig

 

[lowviz]

For the math teacher:

Off-by-one error - Wikipedia, the free encyclopedia

Classic programming problem that even uses the name "fencepost".

Think it through, the problem said property line not fenced-in. Start with the minimum possible situation. If you only had an 8' property line, you would need one set of rails but two posts -one at each end to hold the rail up. If you close the fence, it encircles your property and you don't need the extra post.

(N-1)*8 =L

(N-5-1)*10 =L

equate them:

(N-1)*8 = (N-5-1)*10

8N -8 = 10N -60

10N - 8N = 60 - 8

2N = 52

N = 26


-or just go with what awap said in post #2

 

[miked]

I agree with 26-same logic, good equations awap and lowviz
The end post is the tricky one!
You might need to draw a picture for tyhe teacher. (no offense intended to the teacher).

 

[SC_Hoaty]

I gotta ask since my 6th grade education was also from the state of NJ. What school district/town? NJ has obscene property taxes to ensure a "thorough and efficient" education. Someone is wasting their hard earned money on that teacher.

 

[Karibelle]

Guys thanks - agree 100% with the awnser of 26 but when the math teacher told my daughter it was 25 I figured if I am wrong I can never go on a dive again as all the tennants of my nitrox and pressure calculations would fall flat.

Craig

I know this started out as a mathematical problem, but you mean "tenet" - cannot help myself correcting the word usage issue that has arisen. :blinking:

kari