2009 SC Marathon (3 Viewers)

[Amogh]

There is a similar thread for the HSC, so I figured we should have one for the SC. This thread isn't limited to Maths (Any SC topic)

How To Play:
The first person asks a question (maybe one you've had trouble with). The next person answers it then posts another question for the next person then so on.

Tip:
If you feel an area is your weakness then try asking a question on this area to see others responses to it which may help you in your understanding.

1st Question:
Find the difference between the sum of all even numbers and the sum of all odd numbers, between 1 and 100.

Edit: Maybe we should start with something easier?
1st Question:
A coin is tossed and a standard die rolled. What is the probability of obtaining a head and a number less than 5?

 

[ninetypercent]

lol I'm not allowed to answer

 

[Amogh]

lol I'm not allowed to answer

lol doesnt matter.
join in :uhhuh:
although nothing really has started yet...

 

[occer]

5 / 12 ?

Someone do a question for me, I'm too tired to think.

 

[Riot09]

kim is washing up after a party.there are 45 glasses,20 plates,15 mugs.if 10 glasses,5plates and 5 mugs have already been washed and things are taken at random wha is the chace that the next thing washed will be plate?

a) one-third b) one quarter c) 1/6 d) 7/12 please include working out and a explanation thank you

p.s someone should start a science,english,geo-hist marathon aswell.

 

[Omnipotence]

kim is washing up after a party.there are 45 glasses,20 plates,15 mugs.if 10 glasses,5plates and 5 mugs have already been washed and things are taken at random wha is the chace that the next thing washed will be plate?

a) one-third b) one quarter c) 1/6 d) 7/12 please include working out and a explanation thank you

p.s someone should start a science,english,geo-hist marathon aswell.

1. Initially it was 45 glasses, 20 plates and 15 mugs. Which adds up to 80.
She had already cleaned 10 glasses, 5 plates and 5 mugs. Which adds up to 20.
2. 80 - 20 = 60
3. 20 plates - 5 plates = 15
4. 15/60 = 1/4 = B

Question. (Taken from Amogh, lets start.)
Find the difference between the sum of all even numbers and the sum of all odd numbers, between 1 and 100.

 

[silence--]

2600

edit: someone else do a question

 

[ninetypercent]

purely made up:
4 apples and 2 oranges cost $5.00. 2 apples and 6 oranges cost $6.00. How much would 3 apples cost?

 

[Hayzazz]

$2.40

Write 2^x = y in logarithm format. I know this, but I can't be bothered thinking of another question.

 

[Riot09]

i think igot the answer

4x+2y=5

2x+6y=6

(1.)times the fist one by 3 to make the y values have the same coefficient.

3(4x+2y=5) =12x+6y=15

(2) minus them both to get rid of the y.
=10x=9,x=9/10

sub that back into e.2=

2(9/10)+6y=6

1.8+6y=6

6y=4.2

y=70c

Therefore its $2.70

is this correct?



tara has a pattern of numbers where she adds 7

6,13,20,27.................

will 93 be in the pattern?

 

[Riot09]

i just cheked my answer and its correct.

 

[FTW]

i think igot the answer

4x+2y=5

2x+6y=6

(1.)times the fist one by 3 to make the y values have the same coefficient.

3(4x+2y=5) =12x+6y=15

(2) minus them both to get rid of the y.
=10x=9,x=9/10

sub that back into e.2=

2(9/10)+6y=6

1.8+6y=6

6y=4.2

y=70c

Therefore its $2.70

is this correct?




i just cheked my answer and its correct.

eh??? i thought 70c time 3 = $2.10

 

[silence--]

^yes, but the answer is still 2.70 because you are using x = apples. y is irrelevant

 

[Hayzazz]

i think igot the answer

4x+2y=5

2x+6y=6

(1.)times the fist one by 3 to make the y values have the same coefficient.

3(4x+2y=5) =12x+6y=15

(2) minus them both to get rid of the y.
=10x=9,x=9/10

sub that back into e.2=

2(9/10)+6y=6

1.8+6y=6

6y=4.2

y=70c

Therefore its $2.70

is this correct?



tara has a pattern of numbers where she adds 7

6,13,20,27.................

will 93 be in the pattern?

Huh... I think you did it wrong o___O This is how I did it:

x= apple y= orange

(1) 4x + 2y = 5
(2) 2x + 6y = 6

Now lets multiply (2) by 2, and call it (2a)
(2a) 4x + 12y = 12

Now take away (1) from (2a)
(2a) 4x + 12y = 12
(1) 4x + 2y = 5
10y = 7
y = 0.7

Now sub in 0.7 into y
4x + 2(0.7) = 5
4x + 1.4 = 5
4x = 3.6
x = 0.8

Now we want 3 apples right? 0.8 x 3 = $2.40

 

[silence--]

Huh... I think you did it wrong o___O This is how I did it:

x= apple y= orange

(1) 4x + 2y = 5
(2) 2x + 6y = 6

Now lets multiply (2) by 2, and call it (2a)
(2a) 4x + 12y = 12

Now take away (1) from (2a)
(2a) 4x + 12y = 12
(1) 4x + 2y = 5
10y = 7
y = 0.7

Now sub in 0.7 into y
4x + 2(0.7) = 5
4x + 1.4 = 5
4x = 3.6
x = 0.8

Now we want 3 apples right? 0.8 x 3 = $2.40

thar

 

[FTW]

^yes, but the answer is still 2.70 because you are using x = apples. y is irrelevant

ah rofl, no wonder i was getting so confused as i was going through that question, I had y as apples -.-

 

[Hayzazz]

thar

Oh shit....

Yeah then it is 2.70

...Can't believ I amde I stupid mistake like that ._.

 

[ninetypercent]

tara has a pattern of numbers where she adds 7

6,13,20,27.................

will 93 be in the pattern?

93 - 13 = 80.. this is not divisible by 7. hence, 93 will not be in the pattern.

Write 2^x = y in logarithm format. I know this, but I can't be bothered thinking of another question.

This is not in the Sc. but for those interested, the answer is log(2)y = x

New question:

The hypotenuse of a triangle is 25 cm. The length of the other sides is 3x + 3 and x. Find the value of x

 

[Official]

tara has a pattern of numbers where she adds 7

6,13,20,27.................

will 93 be in the pattern?

93 - 13 = 80.. this is not divisible by 7. hence, 93 will not be in the pattern.

Write 2^x = y in logarithm format. I know this, but I can't be bothered thinking of another question.

This is not in the Sc. but for those interested, the answer is log(2)y = x

New question:

The hypotenuse of a triangle is 25 cm. The length of the other sides is 3x + 3 and x. Find the value of x

25^2 = (3x+3)^2 + x^2

625 = 10x^2 + 18x + 9

10x^2 + 18x - 616 = 0

x = [-18 +- root(24964)]/20 (root formula)

= 140/20 OR -176/20

-176/20 is trivial (x < 0 )

x = 140/20 = 7.

New Question: log(a)b = 0.9, log(a)c = 1.8 where a is the base,

Using this fact, determine the value of log(a)(bc)^2

 

[Hayzazz]

log(a)b + log(a)c = log(a)(bc) = 0.9 + 1.8 = 2.7
log(a)(bc)^2 = 2log(a)(bc) = 2 x 2.7 = 5.4

I hope I remembered my log rules correctly ._.

Ok whats 2^x = y in logorithm form?