Mathematics: Post your doubts here!

[ZainH]

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s12_ms_12.pdf
Q5) ii)

Step by step w/ explanation if possible please x)

 

[GorgeousEyes]

link please?

http://papers.xtremepapers.com/CIE/...S Level/Mathematics (9709)/9709_s10_qp_12.pdf

 

[GorgeousEyes]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s12_ms_12.pdf
Q5) ii)

Step by step w/ explanation if possible please x)

Since you get no i , it's now will be as easy as a cake how ? .. if you look at ii you will find that it looks like i but there's a difference which is 2 .. so you take the tan+1/tan all times 2 = 1+3tan ..
2(tanx+1/tanx)=1+3tanx
2tanx+2/tanx=1+3tanx
so it will be .. 2 tansquare +2 =tan+3tansquare
then .. tansquare+tan-2 .

 

[falcon678]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_s10_qp_12.pdf

itz an arthematic progresion....
a=100
d=5
number of terms= (300-100)/2 +1=41

sum of 41 terms=(41/2)[2x100 + (41-1)5=8200

 

[PhyZac]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w12_qp_63.pdf
Could anyone please help me with qn no. 6 (a)? I don't understand the marking scheme.
Thanks

PhyZac Dug

if twins are there..confirmed 2 girls
and boys are 6C2

if no twins so u take 5C2 (becuase girls are 7 and minus 2 twins so left 5 )
and that into 6C2 of the boys

therefore 6C2 + 6C2 x 5C2

 

[ZainH]

Since you get no i , it's now will be as easy as a cake how ? .. if you look at ii you will find that it looks like i but there's a difference which is 2 .. so you take the tan+1/tan all times 2 = 1+3tan ..
2(tanx+1/tanx)=1+3tanx
2tanx+2/tanx=1+3tanx
so it will be .. 2 tansquare +2 =tan+3tansquare
then .. tansquare+tan-2 .

Oh wow, how did I not notice that? Thanks ;D

 

[GorgeousEyes]

itz an arthematic progresion....
a=100
d=5
number of terms= (300-100)/2 +1=41

sum of 41 terms=(41/2)[2x100 + (41-1)5=8200

4rm where did you get 300-100 /2+1 ?

 

[GorgeousEyes]

Oh wow, how did I not notice that? Thanks ;D

welcome

 

[falcon678]

4rm where did you get 300-100 /2+1 ?

eeeps it waz (300-100)/5 +1
well ummm it said the terms between 300 n 100...thus there r 2oo terms b/t found by subtracting them...n since there is a gap of 5...v divide them by 5....it also said inclusive of 100 n 300...since 300 comes withn tht 200....v ve to add 1 for 100....

i hope u got it...m not much of explainer....

 

[ahmed abdulla]

the ball travel the first time once...then twice after ward...so u multiply with 2 but u minus the first 2 meters

bro it isnt because its first term ....
when you write the sum it comes ,..... 2 + 4*0.75 +4*0.75^2..... so take 2 out to make "a" same ... it can be 4-2 .... replacing the first 2 by 4 .... and minusing from two...

 

[GorgeousEyes]

eeeps it waz (300-100)/5 +1
well ummm it said the terms between 300 n 100...thus there r 2oo terms b/t found by subtracting them...n since there is a gap of 5...v divide them by 5....it also said inclusive of 100 n 300...since 300 comes withn tht 200....v ve to add 1 for 100....

i hope u got it...m not much of explainer....

sorry but i can't get it

 

[salvatore]

if twins are there..confirmed 2 girls
and boys are 6C2

if no twins so u take 5C2 (becuase girls are 7 and minus 2 twins so left 5 )
and that into 6C2 of the boys

therefore 6C2 + 6C2 x 5C2

Thank you for your reply..

I don't get one point here.. if the twins are there, won't the combination be 7C2 (of the girls) X 6C2 (of the boys)?
Why have you omitted the combination of the girls?

 

[syed1995]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w12_qp_63.pdf
Could anyone please help me with qn no. 6 (a)? I don't understand the marking scheme.
Thanks

PhyZac Dug

finally a stats question...

Total Girls 7
Total Boys 6

2 Boys and 2 girls need to be chosen .. while 2 girls are as such that either they are both in the team or not in the team.

Boys And Twins in Team ( Since there are just 2 team members to be chosen and both will be those 2 twins)
6C2 * 2C2

Boys and Twins Not in Team ( Since there are 7 total girls ... total - 2 twins = 5 girls in total left to choose from)
6C2 * 5C2

Total ways = 165 Ways

 

[PhyZac]

Thank you for your reply..

I don't get one point here.. if the twins are there, won't the combination be 7C2 (of the girls) X 6C2 (of the boys)?
Why have you omitted the combination of the girls?

see what syed1995 wrote.
And I will tell my reply to ur question.

we need 2 girls...and the are 5 normal girls and 2 twin sisters.
If we are to choose the 2 twin sisters. then the girls are confirmed, like there are no more to choose.

If we dont take the twin..we have 5 left...and we take 2 thus 5C2
Hope u get it.

 

[PhyZac]

bro it isnt because its first term ....
when you write the sum it comes ,..... 2 + 4*0.75 +4*0.75^2..... so take 2 out to make "a" same ... it can be 4-2 .... replacing the first 2 by 4 .... and minusing from two...

Sorry, i dint really get you. But i will state my point
Ignore everything for now ,

the answer plainly would have been.
[2(1-0.75^n)/1-0.75]
[8-8(0.75^n)]

And now if you agree to this, next step is to know that the ball travel each step twice, Up and Down so answer will be
[8-8(0.75^n)] x 2
16 - 16(0.75^n)

And now if you agree to this, next step is to know that the first time ball moved down only and not up, so we have to minus 2 meters. Therefore what ever the value 16 - 16(0.75^n) this indicates we have to minus 2 meter

therfore
16 - 16(0.75^n) - 2
14 - 16(o.75^n)

I really hope u get me now.

 

[syed1995]

i can't get why did we do this --> OB = OA + OC

This is a rule... known as a parallelogram rule of vectors..

this is because both the opposite sides of the parallelogram are equal. Like this

a + b = c

 

[GorgeousEyes]

This is a rule... known as a parallelogram rule of vectors..

this is because both the opposite sides of the parallelogram are equal. Like this

a + b = c

Thank youuuu

 

[prekshya]

w-06-qp-6 no. 6 ii help plzz..

 

[syed1995]

sorry but i can't get it

To find number of terms you can do use this formulae. d = (l-a)/(n-1)

You need to keep in mind words like inclusive and non inclusive..

Where d is difference l is last term a is first term and n is total number of terms..

so 5 = (300-100)/n-1
n-1 = 200/5
n-1 = 40
n = 41

 

[PhyZac]

w-06-qp-6 no. 6 ii help plzz..

6 men 3 women
no women beside each other
thus
_M_M_M_M_M_M_
u see, i made blanks between men, and women can choose any of these blanks.
therefore
6! x 7P3 ( 6! because u rearrange the 6 men) (7P3, because out of these 7 blanks, 3 are permutated depeneding on where will 3 women stay)
answer = 151200