7th grade math question. Help please

[baddog]

7th grade math bites!
3 picnickers came upon a pile of watermelons. The first picnicker took half of all the watermelons plus a half of a watermelon. The second picnicker took half of what was left plus a half of a watermelon. The third picnicker took half of what was left plus a half a watermelon. There were 15 watermelons left. How many watermelons were in the original pile?

122.5?

[RyuLion]

Borked FTWW!!

[FlexxAeon]

63

and "fuck you", in advance

[Shoehorn!]

Seven.

[RyuLion]

63

and "fuck you", in advance

[EddyTheDog]

125......

[asdasd]

I'm not reading that brainwashed shit.

[Shotsie]

63

and "fuck you", in advance

How did you come up with that number?

[EddyTheDog]

125/2 - .5 = 62

62/2 - .5 = 30.5

30/2 - .5 = 15

I think

[bean-aid]

shit... need to start again

[FlexxAeon]

How did you come up with that number?

math, bitch

[FlexxAeon]

math, bitch

15 = ((x/2 - 0.5) / 2) - 0.5

[bean-aid]

ahhh... too late for me

[d-null]

127 watermelons

[Matyko]

127 is the correct answer, it took me like 10 minutes in the morning before coffee... :P

[EddyTheDog]

127 watermelons

Yep - It is 127 not 125....

[_Richard_]

123 err 127 gaa

8char

[baddog]

127 is the correct answer, it took me like 10 minutes in the morning before coffee... :P

127 seems to be the new answer they are coming up with as well, can you show your math?

I proved it is right, I just don't know how you got there.

[FlexxAeon]

15 = ((x/2 - 0.5) / 2) - 0.5

bleh i rushed

15 = ((((x/2 - 0.5) / 2) - 0.5 ) / 2) - 0.5

127

[martinsc]

how big are the melons?

[Matyko]

127 seems to be the new answer they are coming up with as well, can you show your math?

I admit I tried to make it the usual way of math but I failed with that. Then I just did the plain pen and paper solution starting from backwards: to have 15 left I need 31 watermelons, so when the half of it is gone, minus a half 15 will remain. 31 is double the 15 plus one. tested this for the next level and it worked: double 31 plus one: 63 is next level. counted back: worked. 63x2 + 1 = 127 for the last level, counted back, worked, tadaaam! I know it might sound stupid.. :P

[baddog]

I admit I tried to make it the usual way of math but I failed with that. Then I just did the plain pen and paper solution starting from backwards: to have 15 left I need 31 watermelons, so when the half of it is gone, minus a half 15 will remain. 31 is double the 15 plus one. tested this for the next level and it worked: double 31 plus one: 63 is next level. counted back: worked. 63x2 + 1 = 127 for the last level, counted back, worked, tadaaam! I know it might sound stupid.. :P

Actually, that is how I was trying to do it to, but I was pretty sure the teacher was not going to accept that explanation.

[raymor]

I admit I tried to make it the usual way of math but I failed with that. Then I just did the plain pen and paper solution starting from backwards: to have 15 left I need 31 watermelons, so when the half of it is gone, minus a half 15 will remain. 31 is double the 15 plus one. tested this for the next level and it worked: double 31 plus one: 63 is next level. counted back: worked. 63x2 + 1 = 127 for the last level, counted back, worked, tadaaam! I know it might sound stupid.. :P

That's how I would do it. Though I COULD do it forwards in my head, I think, I'm always up for cheating by doing it backwards.

[bean-aid]

From the beginning

Z = total watermelons

student 1 = a
student 2 = b
student 3 = c

a has .5Z + .5
b has .5a + .5
c has .5b + .5
c has 15
b = 29
a = 57
z = 113

113 total...

damn... that's wrong again... lol

[Matyko]

Actually, that is how I was trying to do it to, but I was pretty sure the teacher was not going to accept that explanation.

http://www.youtube.com/watch?v=YR5ApYxkU-U#t=2m47s

[EddyTheDog]

That's how I would do it. Though I COULD do it forwards in my head, I think, I'm always up for cheating by doing it backwards.

Is doing it backwards cheating?

[Shotsie]

From the beginning

Z = total watermelons

student 1 = a
student 2 = b
student 3 = c

a has .5Z + .5
b has .5a + .5
c has .5b + .5
c has 15
b = 29
a = 57
z = 113

113 total...

[EddyTheDog]

[baddog]

From the beginning

Z = total watermelons

student 1 = a
student 2 = b
student 3 = c

a has .5Z + .5
b has .5a + .5
c has .5b + .5
c has 15
b = 29
a = 57
z = 113

113 total...

You are forgetting that there are 15 left over, not the 3rd kid got 15. With 113 b = 28.5

[bean-aid]

a = z*.5 -.5 (what is left)
b = a*.5 -.5 (what is left)
c = b*.5 -.5 (what is left)
c = 15
b=31
a=63
z=127

[d-null]

x= total watermelons
a= first person
b= second person
c= third person

x-a-b-c=15
a=0.5x+0.5
b=(x-a)*0.5+0.5
c=(x-a-b)*0.5+0.5

127 watermelons

[bean-aid]

yup... lol.

I got it at the end...

[epitome]

I just ate a quarter of a watermelon.

Time to start over.

[_Richard_]

[bean-aid]

Don't be mean... this is what I enjoy on a thirsty thursday A good math question to put sparks in the brain

[KRosh]

x=x/2 - 1/2


Transform to Algebra..B represents before the watermelons were taken and A represents after they are taken

B/2 - 1/2 = A.

solve for B
2*A + 1 = B.


Now work backwards...

Value of x:15

2*15+1=31

2*32+1=63

2*63+1=127

Answer = 127

[baddog]

x=x/2 - 1/2


Transform to Algebra..B represents before the watermelons were taken and A represents after they are taken

B/2 - 1/2 = A.

solve for B
2*A + 1 = B.


Now work backwards...

Value of x:15

2*15+1=31

2*32+1=63

2*63+1=127

Answer = 127

I will just call you the next time.

[Double trouble]

41 ?

[Deej]

its that damned half a melon each time that most dont consider not being a portion of the half...

[Adraco]

I admit I tried to make it the usual way of math but I failed with that. Then I just did the plain pen and paper solution starting from backwards: to have 15 left I need 31 watermelons, so when the half of it is gone, minus a half 15 will remain. 31 is double the 15 plus one. tested this for the next level and it worked: double 31 plus one: 63 is next level. counted back: worked. 63x2 + 1 = 127 for the last level, counted back, worked, tadaaam! I know it might sound stupid.. :P

This is how I did too, 127 is correct.

[OY]

Thanks Baddog - this just reminded me on what year my math grade began to deteriorate. Pretty much exactly in 7th grade.....

[RazorSharpe]

erm - it can't possibly be 127, can it? 3 people took 1/2 a watermelon so there has to be a half left over but what is left over is 15 FULL watermelons!!

[EddyTheDog]

erm - it can't possibly be 127, can it? 3 people took 1/2 a watermelon so there has to be a half left over but what is left over is 15 FULL watermelons!!

It works out.

127/2 = 63.5

63.5 - 0.5 = 63

63/2 = 31.5

31.5 - 0.5 = 31

31/2 - 15.5

15.5 - 0.5 = 15

[DWB]

I have always been bad with math questions like that. So looks like I'm going back to the 7th grade.

But the questions to ask is, have any of you applied such a question in real life?

[RazorSharpe]

nevermind - silly me! figured it out now!!

[Matyko]

I have always been bad with math questions like that. So looks like I'm going back to the 7th grade.

But the questions to ask is, have any of you applied such a question in real life?

I think it doesn't really matter and obviously there's no use of such knowledge in real life, but this actually can make a kid Think and use his or her logic, which is not bad.

[L-Pink]

You really need to start dating older women that don't have homework.

.

[DEA]

fuck math...lets eat watermelon

[raymor]

I think it doesn't really matter and obviously there's no use of such knowledge in real life, but this actually can make a kid Think and use his or her logic, which is not bad.

I use it all day long. There were 127 members. One username was used from three IPs. One third of all IPs are mobiles ... Whose the thief?


Jack jacked off on your site three times over the weekend. He downloaded 700 MB. Carl logged in twice but and downloaded half again as much ...
Are any of them downloading too much more than normal, indicating they are downloading to post it somewhere rather than jacking off?

Vladimir has 2000 proxies. Each proxy can brute force 12 times per minute ...

[_Richard_]

Don't be mean... this is what I enjoy on a thirsty thursday A good math question to put sparks in the brain

hey i fucked up too, forgot to take away the last half a watermelon

that's a funny picture.. come on..