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# A line passes through point p(1,1) and q(100,1000). How many other poi

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A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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28 Jan 2015, 07:00
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95% (hard)

Question Stats:

35% (02:20) correct 65% (02:25) wrong based on 206 sessions

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A line passes through point p(1,1) and q(100,1000). How many other points with integer co-ordinates are on the line and strictly between points p and q ?

a) 0
b) 2
c) 3
d) 8
e) 9
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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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28 Jan 2015, 07:23
2
ans D.....
p(1,1) and q(100,1000)... so the ratio in which the increase is ,increase of x by 10 results in increase of 100 in y coord..
so for x, there are 8 such points for which y is also int...
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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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28 Jan 2015, 08:09
1
chetan2u wrote:
ans D.....
p(1,1) and q(100,1000)... so the ratio in which the increase is ,increase of x by 10 results in increase of 100 in y coord..
so for x, there are 8 such points for which y is also int...

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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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28 Jan 2015, 08:25
2
DesiGmat wrote:
chetan2u wrote:
ans D.....
p(1,1) and q(100,1000)... so the ratio in which the increase is ,increase of x by 10 results in increase of 100 in y coord..
so for x, there are 8 such points for which y is also int...

hi...
the Y coord is increasing by(1000-1) or999 as x increases by (100-1) or 99..
so the ratio of increase is 99:999 or 11:111...
it means with every increase of x by 11 , y increases by 111..
so the value of 12(1+11) will have y as 112(1+111).. 23(12+11) will have 223(112+111) and so on till 89 will have 889..
value of x as 1 and 100 is not taken so 8 values 12,23,34,45,56,67,78,89 with corresponding int values for Y
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1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html

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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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29 Jan 2015, 04:49
3
Let's say point p is at the origin and q is at the (99,999) (this does not change the problem).
The line pq has the equation y =$$\frac{999}{99}x$$= $$\frac{111}{11}x$$ .

Now the co-ordinates of y will be integer, when x takes the value of 11,22,33,44,55,66,77,88.

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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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29 Jan 2015, 06:11
Line equation y = mx + c....Using the inform...m = 111/11....so y = 111/11x + c......put y=x= 1....c = -100/11
Line eqn :-11y = 111x - 100......x = (11y+100)/111...limit x till 100....only 8 values permissible
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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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07 Mar 2015, 23:50
Hi,

I didnt get the solution.Why can't 99 also be the value ??
When x is 99 ,y can still be an integer..??
Can some1 please explain the problem
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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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30 Jun 2015, 06:03
the slope we will get as 11/111.
Then equation of the line y=11/111x+c
if we take for every mulitple of 111, the value of y is integer, then we will have 9 values.

Can someone pls tell me where i am going wrong?
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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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10 Aug 2015, 20:54
jayanthjanardhan wrote:
the slope we will get as 11/111.
Then equation of the line y=11/111x+c
if we take for every mulitple of 111, the value of y is integer, then we will have 9 values.

Can someone pls tell me where i am going wrong?

Hi,

The error is that c is not an integer. Am I right in suggesting that you have assumed c to be an integer?
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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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17 Aug 2015, 11:14
The slope is y2-y1/x2-x1. So, it is 1000-1/100-1 = 999/99 = 111/11

Also, the value of C needs to be calculated (to check whether it is integer). In this case, the value of C is not an integer = -100/11.

Hope this helps.
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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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18 Sep 2015, 03:58
The slope is y2-y1/x2-x1. So, it is 1000-1/100-1 = 999/99 = 111/11

Also, the value of C needs to be calculated (to check whether it is integer). In this case, the value of C is not an integer = -100/11.

Hope this helps.

Hi Aryama,

Can you extend your explanation further
I mean now we have got the equation of the line as

y= (11/111)x -100/11

Now how to go ahead with this from here
What values one should place here to get integer value of y

Thanks
Kani
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A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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18 Sep 2015, 13:53
2
2
Hi folks, here is how i solved the problem :

From the two point coordinates, we obtain the following equation Y= (111/11)*X - 100/11; This equation can be written as follow : (111*X - 100)/11 or More better (100(X-1) + 11 X)/11 .

Now the problem here is that we should obtain an INTEGER Y, in other words (100(X-1) + 11 X) should be divisible by 11.

11X is obviously divisible by 11 so we can neglect it, now our unique friend is 100(X-1) which should be divisible by 11.

X ranges from 1 to 100 , thus the possible values for X to be divisible by 11 are : 12, 23,34,45,56,67,78,89 . So we have 8 values, thus Answer (D) is correct.

Hope it helps
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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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21 Sep 2015, 22:14
1
Slope is calculated by using the formula :

m = y2-y1/x2-x1

Slope intercept format (Equation of the line)

Y = mx+c

In this equation substitute the values of " m "and one of the given coordinates (x,y) to get the value of C.

c= -100/11

So y becomes y=(111/11)x-100/11

= (111x-100) /11

X =1 So we get Y = 1 (given co-ordinates). We want values between (1,1) and (100, 1000)

The next values of X that make Y as integer is 11 (divisor is 11) more than the first value.

12,23 (12+11),34,45,56,67,78,89 = Total 8 values.
HOPE IT HELPS!!
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Re: A line passes through point p(1,1) and q(100,1000). How many other poi  [#permalink]

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