urgent questions from BB!!!

[mystic87]

I just finished Problem Solving test1 from BB, and mannn was it hard!
Need some help here guys...


1. A straight raod runs from North to South. It has two turnings towards east and three turnings towards west. In how many ways can a person coming from east get on the road and go west?
A.2
B.3
C.9
D.6
E.5
(I really dont understand this turning at all, especially just two turns from a north-south road to face east)

**2. How many heptagons can be drawn by joining the vertices of a polygon with 10 sides?
A.562
B.120
C.105
D.400
E.282

OKAY, BB had other questions like this on their first Word problem set. PLEASE HELP!!! there's gotta be some kinda way to do this...

3.A teacher prepares a test. She gives 5 objective type questions out of which 4 have to be answered. Find the total ways in which they can be answered if the first 2 questions have 3 choices and the last 3 have 4 choices.
A.255
B.816
C.192
D.100
E.144

I thought this question was pretty straight forward: just list all the possiblities.
3x3x4x4 =126
3x4x4x4 =192
4x4x4x4 = 256
and add them. BUUUTT that's apparently incorrect.

4. finding the number of words which can be formed by using the letters of the word EQUATION if each word has to start with a vowel.
Answer = 25200
WHY??
----------------------------------------------------------------------
ANSWERS:
1.D 2.B 3.D

[DUALUM]

1. 3*2=6
2.10C7=120
3. Either First 2+ 2 from last OR 1 from first 2+3 from last 3.
Choose first 2 + 2 from last 3 in 2C2*3C2=3 ways. They can be answered in 3*3*4*4 multiplied by 3 =432
Choose 1 from first+3 from last 3 in 2 ways. Answer in 3*4*4*4 multiplied by 2=384
Total 432+384=816
4. The first place can be taken by any of the 5 vowels. 2nd place by any of rest 7, the next by any of 6.............
So 5*7*6*5*4*3*2=25200

[mystic87]

Thanks Dualum! wow, i feel stupid. this whole time i was thinking "turnings" meant streat corners at intersections and limiting myself only to 90 degree turns.

Heptagon = 7sided polygon.

Here's a similar question to #2:
If you connected all the vertices of a heptagon, how many quadrilaterals will you have? (quadrilateral=4-sided)

answer: 35

[mystic87]

i got the last question by trial and error but i dont think that'll work for #2. there's just gotta be some way to solve it!

[DUALUM]

If you connected all the vertices of a heptagon, how many quadrilaterals will you have? (quadrilateral=4-sided)

answer: 120


Are you sure the ans is 120? I get 35!

[DUALUM]

I gave the explanations. Plz check.

[mystic87]

What's the logic behind using combination?

[DUALUM]

Combination - choose/select and order is not important. You are choosing any 4 sides out of the total 7 sides.

[prithibi]

7c4 makes 35 . hw could u find 120. i can't understand

[mystic87]

sorry prithibi, that's my mistake for confusing you. I actually put down the wrong answer. 7C4 is the correct answer to how many quadrilaterals you can find in a heptagon