Homework Help Plz

[monkey_henry]

I hope that this is in the right forum, but I need help on some math homework.
Ok, here are the questions:
1)The sum of seven consecutive positive integers is always
A) odd B) a multiple of 7 C) even D) a multiple of 4 E) a multiple of 3
I think its B but im not sure.

2) Kalyn writes down all of the integers from 1 to 1000 that have 4 as the sum of their digits. If a/b (in lowest terms) is the fraction of these numbers that are prime, then a+b is
A)5 B)4 C)15 D) 26 E)19
I have no idea about this one.

3) Four identical isosceles triangles border a square of side 6 cm. When the four triangles are folded up they meet at a point to form a pyramid with a square base. If the height of this pyramid is 4 cm, the total area of the four triangles and the square is
A) 84 cm squared B) 98 cm squared C) 96 cm squared D) 108 cm squared E) 90 cm squared
I think it is D but again im not sure.

Plz post or pm me if u can help or give me the answer thanx!

[thorax_the_basher]

what math are you in?, just woundering cuz im in 11th grade and dont think ive ever learned anything about that. sorry i cant be much more help but will ask my mom/ dad when they get home and see if they have any idea. Thak ok with you?

[monkey_henry]

No prob thanx for for helping.
Get back to me if u find the answer.
BTW im in grade eight

[dancingmaniac3]

for number 1, write down seven consecutive numbers and see. Its easier than it looks, it really is.

ex:

1+2+3+4+5+6+7 = 28

28 = a multiple of 7, 4, and is even.

so that counts out A and E.

so try a new seven numbers:

2+3+4+5+6+7+8 = 35

35 = odd, so that counts out C.
35 = multiple of 7, so that leaves B.
35 = not a multiple of 4, counting out D. Leaving you with choice B. A multiple of 7. yay.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[Reach]

#1.

B

#2. There are 15 of them.

1/3 of them are prime, so the answer is B

#3. The answer is A. 36+48 = 84

[Shashakiro]

uhh yeah 1 is B but I have no idea how what Reach posted has anything to do with the question =P

P.S. #3 is A.

4 cm altitude * 4 triangles * 6 base / 2 = 48
6^2 = 36

add to get 84

[Reach]

I thought the consecutive ment that it was repeating. I guess it doesn't matter, the answer is the same xD

Oh and the answer is 84 to the last one. I thought it ment the area inside, oops.

[Shashakiro]

The volume would have been 36 by the way, if that was the question =P

[monkey_henry]

Originally Posted by Shashakiro

uhh yeah 1 is B but I have no idea how what Reach posted has anything to do with the question =P

P.S. #3 is A.

4 cm altitude * 4 triangles * 6 base / 2 = 48
6^2 = 36

add to get 84

Thats what i thought too but i though that seemed too easy.
i dont think that the altitude is 4 cm though. because i dont think the height of the pyramid is the altitude of the triangles though.
EDIT and my friend said something about the altitudes of the triangles being 6 cm.

[thorax_the_basher]

#2 is B like they said because there are 15 total, 5 are prime, so thats 1/3 in terms of a and b, so a+b=4

[monkey_henry]

yeah i know the equations just not sure of the answer.

[Shashakiro]

Oh nvm. Silly mistake. ><

#3 is 96, so C. We were all wrong before XD

P.S. #3 is an awfully hard problem for 8th grade o.O

[monkey_henry]

can you explain how? and yes i know this is hard for 8th grade thats y i needed help. the first one i wanted to confirm my answer and i didnt understand the second one.

[Reach]

Originally Posted by Shashakiro

Oh nvm. Silly mistake. ><

#3 is 96, so C. We were all wrong before XD

P.S. #3 is an awfully hard problem for 8th grade o.O

Sneaky question.

Owned by rushing through grade 8 math. arg.

[monkey_henry]

lol im pretty sure this isnt 8th grade material i think this is just a bonus question.

[Shashakiro]

Yeah, when he said 8th grade math I was like "these problems can't possibly take more than 2 steps" so I made bad assumptions =(

But yeah, it's definitely C, 96. Not a bad problem, really...

These look like maybe they come from an AMC 8...they're all that sort of problem =)

EDIT: Height of pyramid, half the side length of the square, and the altitude of a triangle make a 3-4-5 triangle. So the triangles have an altitude of 5 and a base of 6. That gives each triangle an area of 5*6/2 = 15, so with 4 triangles and the 6 x 6 square, the answer is 15 * 4 + 6 * 6 = 96.

[monkey_henry]

Cool ok i got another question in a couple of minutes=D
P.S. i think it is the amc or something like it anyways.

[esupin]

I took the AMCs. I'm assuming you're taking the 8 or the 10. I should have made it to the next round on the 12s, but I F'd uf one question.

[Shashakiro]

I always get to the AIME...but after that it's over for me, the AIME is just way too hard =(

[monkey_henry]

Question Four:
Ray's financial institution publishes a list of service charges as shown in the table. (see below) For her first twenty five transactions, she uses Autodebit three times as often as she writes cheques. She also writes as many cheques as she makes cash withdrawals. After his twenty-fifth transaction, she begins to make single transactions. What is the smallest number of transactions he needs to make so that his monthly service charges will exceed the $15.95 'all-in-one' fee?

Service Fee per Item
Cheque $0.50
Autodebit $0.60
Cash Withdrawal $0.45
All-in-one' fee is $ 15.95

A) 29 B) 30 C) 27 D) 28 E) 31

I dont quite understand this one.
sry i couldnt make the chart so well.