7th grade math question. Help please
 

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?

Borked FTWW!!

63

and "fuck you", in advance :1orglaugh

Seven. :2 cents:

:2 cents::2 cents::thumbsup:1orglaugh

125......

I'm not reading that brainwashed shit.

http://i.imgur.com/OdkDx.jpg

How did you come up with that number?

125/2 - .5 = 62

62/2 - .5 = 30.5

30/2 - .5 = 15

I think

shit... need to start again

math, bitch :1orglaugh

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

ahhh... too late for me

127 watermelons

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

Yep - It is 127 not 125....

123 err 127 gaa

8char

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.

:1orglaugh bleh i rushed

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

127

how big are the melons?

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 :pimp

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. :1orglaugh

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.

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

Is doing it backwards cheating?

:1orglaugh:1orglaugh:1orglaugh

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

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

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

yup... lol.

I got it at the end... :thumbsup

I just ate a quarter of a watermelon.

Time to start over.

:1orglaugh:1orglaugh:1orglaugh

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

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
:upsidedow

I will just call you the next time.

41 ? :1orglaugh

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

This is how I did too, 127 is correct.