Mathematics: Post your doubts here!

[student2]

ny1?

 

[Saly Elkady]

Given that, Sum of First and Fourth term is 70 and sum of Second and Third term is 60, so there's no way the sum to infinity be 10 or 7.

From the answer i posted,

r = 2/3 or 3/2
When r = 2/3,
a = 54
T1 = 54
T4 = 16
Hence T1 + T4 = 70

Again, When r = 3/2

T1 = 16
T4 = 54
Hence T1 + T4 = 70

Thanks

 

[areeba240]

how to get the value of z as 0.674? and why +_0.674? plzz help

 

[areeba240]

need a explanation on how to the height and the thickness
how will i know that graph X will be from 10 to 50
and will be higher or lower the the other graphs? plzz help

 

[Bishnu Dev]

View attachment 62168
View attachment 62169
need a explanation on how to the height and the thickness
how will i know that graph X will be from 10 to 50
and will be higher or lower the the other graphs? plzz help

Well i don't have much information however for this problem, i do guess work.
Variance gives standard deviation. Standard deviation means average deviation of values from the mean value. For X, SD = 7. Since it is an average, you have to make it more spread than keeping the boundary within 7 from the mean. Remember to make both sides equal from the mean.

For Z and Y, the variance is less. Hence less spread. But the height is greater because AREA UNDER X = AREA UNDER Y and AREA UNDER Y = AREA UNDER Z.

 

[Bishnu Dev]

View attachment 62166
View attachment 62167
how to get the value of z as 0.674? and why +_0.674? plzz help

You need to find the Standard deviation. Given that, 63 is upper quartile. Hence P (x < 63) = 0.75 (Use Normal distribution table to get 0.674)

 

[areeba240]

Well i don't have much information however for this problem, i do guess work.
Variance gives standard deviation. Standard deviation means average deviation of values from the mean value. For X, SD = 7. Since it is an average, you have to make it more spread than keeping the boundary within 7 from the mean. Remember to make both sides equal from the mean.

For Z and Y, the variance is less. Hence less spread. But the height is greater because AREA UNDER X = AREA UNDER Y and AREA UNDER Y = AREA UNDER Z.

i didnt understand

 

[Bishnu Dev]

i didnt understand

Well the spread part is like this.... You've SD, right? Recall that the graph is symmetrical and mean is at the middle. Standard deviation gives the measure of spread. From the definition, Standard deviation is the average deviation of the values from the mean value. But it is not possible that the minimum value and max value be within 1 standard deviation from the mean. So the minimum value must be less than (Mean - SD). BUT i cannot confirm the actual value where the curve should start from however it must be less than (Mean - SD).

Height Part: We know that the area under each graph must be equal. For Y and Z, the spread is less and to make the area equal to X, we must have to increase the height.

 

[areeba240]

Well the spread part is like this.... You've SD, right? Recall that the graph is symmetrical and mean is at the middle. Standard deviation gives the measure of spread. From the definition, Standard deviation is the average deviation of the values from the mean value. But it is not possible that the minimum value and max value be within 1 standard deviation from the mean. So the minimum value must be less than (Mean - SD). BUT i cannot confirm the actual value where the curve should start from however it must be less than (Mean - SD).

Height Part: We know that the area under each graph must be equal. For Y and Z, the spread is less and to make the area equal to X, we must have to increase the height.

so how will i now that it should from 10 and end at 50?

 

[Bishnu Dev]

so how will i now that it should from 10 and end at 50?

Almost all the values lie within 3 standard deviation from the mean. So 3 * 7 = 21. and 30-21 = 9. similarly, 30+21 = 51. but it's not exact. roughly between 9 to 51

 

[areeba240]

Generally, all the values lie within 3 standard deviation from the mean. So 3 * 7 = 21. and 30-21 = 9. similarly, 30+21 = 51. but it's not exact. roughly between 9 to 51

thanks

 

[areeba240]

9709/w11/63
plzz someone help me out with (i)

 

[areeba240]

9709/w10/63
plzz help

 

[sj0007]

View attachment 62176
9709/w10/63
plzz help

Weight is a random variable and that too a continuous one. The distribution for a continuous random variable is 'normal distribution' (according to what we have studied) with parameters (Mean, variance)........ Just put in some sensible appropriate values for an average of weight of 18 year old girls and for variance just square the standard deviation......
They have said 40-80 for the mean and a standard deviation between 4-15

 

[areeba240]

Weight is a random variable and that too a continuous one. The distribution for a continuous random variable is 'normal distribution' (according to what we have studied) with parameters (Mean, variance)........ Just put in some sensible appropriate values for an average of weight of 18 year old girls and for variance just square the standard deviation......
They have said 40-80 for the mean and a standard deviation between 4-15

so the whole qtn depends on our guess?

 

[sj0007]

so the whole qtn depends on our guess?

Yeah you can say so, more like on an educated guess though

 

[areeba240]

View attachment 62175
9709/w11/63
plzz someone help me out with (i)

plzz help me out with this qtn (i)

 

[Bishnu Dev]

View attachment 62175
9709/w11/63
plzz someone help me out with (i)

the best way to solve this is to find probability, p(m') for males who don't watch Kops are Kids then Final answer would be 1 - p(m')

P(m') = 18/30 * 5/18 = 1/6
Now 1 - P(m') = 5/6

 

[krishnapatelzz]

https://www.facebook.com/Aleveldiscussions/ for A level

 

[amina1300]

https://drive.google.com/file/d/0B7SutyFkNVj5akFiYm84WFFoWTA/view?usp=drivesdk
Solve this? x, y = ??