Maths
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The numbers from 1 to 49 are arranged in a table shown below.
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table lehhh?
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Column 1 2 3 4 5 6 7 1 1 2 3 4 5 6 7 2 8 9 10 11 12 13 14 3 15 16 17 18 19 20 21 Rows 4 22 23 24 25 26 27 28 5 29 30 31 32 33 34 35 6 36 37 38 39 40 41 42 7 43 44 45 46 47 48 49 N X M (a) find the sum of the 7 numbers in the shaded BOLD diagonal.
(b) express x in terms of n where x is the number in the nth row and 1st column.
(c) express m in terms of n where m is the number in the nth row and 4th column.
(d) express the sum S of the 7 numbers in terms of m and n.
(e) if S=714, find the value of n.
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Originally posted by FireIce:
table lehhh?
He is new here, give him sometime.And to TS, what is the question?
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<a href="http://img29.imageshack.us/my.php?image=snapshot200905291.jpg" target="_blank">
hi all pls click on the link to get the photo image of the question just taken, the questions are as below (a) to (e) as reposted by moderator eagle(thanks! bro)
much help kindly appreciated. i'm not good at guessing number patterns, any tips? :>
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Repost:
The numbers from 1 to 49 are arranged in a table shown below.
(a) find the sum of the 7 numbers in the shaded BOLD diagonal.
(b) express x in terms of n where x is the number in the nth row and 1st column.
(c) express m in terms of n where m is the number in the nth row and 4th column.
(d) express the sum S of the 7 numbers in terms of m and n.
(e) if S=714, find the value of n.
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Originally posted by eagle:
Repost:
The numbers from 1 to 49 are arranged in a table shown below.
(a) find the sum of the 7 numbers in the shaded BOLD diagonal.
(b) express x in terms of n where x is the number in the nth row and 1st column.
(c) express m in terms of n where m is the number in the nth row and 4th column.
(d) express the sum S of the 7 numbers in terms of m and n.
(e) if S=714, find the value of n.
Don't just repost, help to solve!
Currently stuck at (d), need some sweets to get my brain moving again.
(a) 175
(b) x = 1 + 7 (n-1)
(c) m = 4 + 7 (n-1)
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busy writing some summary notes for solving common potentiometer questions in H2 Physics la
You sure can do one, jiayou
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Stuck at d as well...
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hey bro forbiddensinner, thanks for yr reply.
was thinking it will be great how you can derive the formula for (b) and (c)
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Originally posted by Divanhot:
hey bro forbiddensinner, thanks for yr reply.
was thinking it will be great how you can derive the formula for (b) and (c)
For ( b ) and ( c ), it is mostly just observation-based.The 1st thing you will have to notice is that the numbers are plus 7 as it move down the row.
Since the 1st no. in column 1 is 1, we take it as a base constant, and then we add 7 ( n - 1 ), where n is the row, to it. The same goes for each and every column.
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Originally posted by dkcx:
Stuck at d as well...
Ok, I chu ma
actually can just express in terms of m
Sum of 7 numbers = (m-24) + (m-16) + (m-8) + m + (m+8) + (m+16) + (m+24) = 7m
And then using this, can solve for e
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Here's another question b4 i go sleep:
Susan stands at edge of cliff, throws a ball upwards. The height of ball above top of cliff in h metres is
h= 8t-5t^2 Q: Susan throws 2nd ball, in exactly same way, 4s after she throws the 1st .
Find how far apart the 2 balls are, 1s after the 2nd ball is thrown.
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Originally posted by eagle:
Ok, I chu ma
actually can just express in terms of m
Sum of 7 numbers = (m-24) + (m-16) + (m-8) + m + (m+8) + (m+16) + (m+24) = 7m
And then using this, can solve for e
I got something like summation of m + n - 4 from 1 to 7.Any ideas on how to simplfy it?
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Originally posted by Forbiddensinner:
I got something like summation of m + n - 4 from 1 to 7.Any ideas on how to simplfy it?
no need so chim ma
the number m is at the centre of the 7 numbers
so is 7m lor
So if express in terms of n, then sum will be using part c's answer
Sum = 7 (4 + 7 (n-1))so part e will be
714 = 7 (4 + 7 (n-1))
4 + 7n - 7 = 102
n = 15 -
Originally posted by Divanhot:
Here's another question b4 i go sleep:
Susan stands at edge of cliff, throws a ball upwards. The height of ball above top of cliff in h metres is
h= 8t-5t^2
Q: Susan throws 2nd ball, in exactly same way, 4s after she throws the 1st .
Find how far apart the 2 balls are, 1s after the 2nd ball is thrown.
height of 1st ball = 8(5) - 5(5)^2 = 40 - 125 = -85m, meaning it is 85m below cliff.height of 2nd ball = 8(1) - 5(1)^2 = 8 - 5 = 3m, meaning it is 3m above cliff.
distance apart = 85m + 3m = 88m
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Originally posted by eagle:
no need so chim ma
the number m is at the centre of the 7 numbers
so is 7m lor
So if express in terms of n, then sum will be using part c's answer
Sum = 7 (4 + 7 (n-1))so part e will be
714 = 7 (4 + 7 (n-1))
4 + 7n - 7 = 102
n = 15
Thanks to you, I see the light.But the question is quite misleading.
What they want is an expression in S and m, followed by another in S and n.
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hi, wonder how come for part (d), we can use 25 as base reference point. m is not equal to 25 right? they r only in same column 4
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Originally posted by Divanhot:
hey bro eagle, i dun understand answer to part (d)
how u get S= 7m. can u illustrate examples to show this, thanks
Here it is :D
Sum of 7 numbers = (m-24) + (m-16) + (m-8) + m + (m+8) + (m+16) + (m+24) = 7m
Try and see the patternHint: In your table, m = 25
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hi bro eagle, i dun understand how we can assume m=25, cuz i thought m is a number in the 4 column but in nth row.
i can c if we use 25 as base reference, we get S=7m= 7*25=175
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try to look at the pattern
m=25 is only an example
it can be 32 or 40 as well, Then u look at the previous numbers and numbers after that
Try to draw out on the table... circle it...
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hi forbiddensinner, can i say we use t=5 for 1st ball distance travelled as the 2nd ball is 4s behind the 1st ball.
so 1s after the 2nd ball is thrown, the 1st ball has travelled 5s?
n y we dun use t=4 for 2nd ball distance travelled
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Originally posted by Divanhot:
hi forbiddensinner, can i say we use t=5 for 1st ball distance travelled as the 2nd ball is 4s behind the 1st ball.
so 1s after the 2nd ball is thrown, the 1st ball has travelled 5s?
n y we dun use t=4 for 2nd ball distance travelled
Yes, we use t=5 as the 2nd ball is 4s behind the 1st ball.
We don't use t=4, and use t=1, as the 2nd ball has only travelled for 1s.
The 'h' formula given in this case has been stated as height above cliff, hence you can safely assume that positive numbers = distance above cliff and negative numbers = distance below cliff.
Thus, you can directly sub in "t" timings.
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hey !! No table is being displayed!!
Check out!~!
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philip
