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Mathematics 14 Online
OpenStudy (saifoo.khan):

Question coming.

OpenStudy (saifoo.khan):

OpenStudy (anonymous):

I can't believe it!!! You really have a doubt?

OpenStudy (saifoo.khan):

Lol @pratu043 .

OpenStudy (unklerhaukus):

odd times odd times even

OpenStudy (anonymous):

Assume w as 5 then try to solve..

OpenStudy (saifoo.khan):

@waterineyes , why 5?

OpenStudy (unklerhaukus):

there is a typo in the question and it is damn hard to read

OpenStudy (foolaroundmath):

Let the w = 2k+1 Then we need the product of (2k+2)(2k-1) Notice that from the two numbers, the larger one is even and is greater than the odd number by 3. Now all you have to do is factor the options, and check if the larger factor is even and is greater than the odd factor by 3 or not

OpenStudy (anonymous):

Okay.. Assume w as 1 3 5 7 and 9 then try to solve..

OpenStudy (saifoo.khan):

@UnkleRhaukus . I didn't typed it. :D

OpenStudy (unklerhaukus):

maybe you should have , then we could read it

OpenStudy (saifoo.khan):

2k + 1 ? How? @FoolAroundMath @waterineyes , ok. just a sec.

OpenStudy (foolaroundmath):

any odd number can be written as an even number + 1 and since 2k is even (if k is a natural number) so consequently, 2k+1 is odd (k is a whole number)

OpenStudy (unklerhaukus):

wait the product is just of two terms , one odd one even

OpenStudy (saifoo.khan):

If w is +ve odd integer, which of the following gives a possible value of the product value of one 1 than w and 2 less than w.

OpenStudy (saifoo.khan):

@UnkleRhaukus ^

OpenStudy (unklerhaukus):

(w+1)(w-2)=

OpenStudy (unklerhaukus):

cannot be even

OpenStudy (callisto):

(w+1)(w-2) = sth If = 0 w^2 - x -2 =0 w = 2, or w=-1 (rejected) if = 10 w^2 - x -2 =10 w = 4 or w =-3 (rejected) if = 18 w^2 - x -2 =18 w = 5 or w =-4 => YES! If = 28 w^2 - x -2 =28 w = 6 or w = -5 (rejected) If = 54 w^2 - x -2 =54 w = 8 or w =07 (rejected)

OpenStudy (anonymous):

w = 5

OpenStudy (anonymous):

How can be w = 2??

OpenStudy (callisto):

w= -7 instead of w=07 for the last one sorry..

OpenStudy (anonymous):

w is an odd positive integer..

OpenStudy (unklerhaukus):

o dear

OpenStudy (callisto):

So, only 18 is the possible answer! @waterineyes

OpenStudy (anonymous):

yes.. 18 is the possible answer for w = 5..

OpenStudy (callisto):

* sth = something..

OpenStudy (saifoo.khan):

Perfect guys. Thanks all. I still owe a medal to @waterineyes , @Callisto and @FoolAroundMath . (:

OpenStudy (unklerhaukus):

take the medal off me i made to many mistakes

OpenStudy (saifoo.khan):

@UnkleRhaukus , atleast you tried. :D

OpenStudy (anonymous):

See, w is an odd integer so it can be 1 3 5 7 9 and so on.. For w = 1, (1 + 1)(1 - 2) = Negative (Ignore) For w = 3, (3 + 1)(3 - 2) = 4 (Not in option) For w = 5, (5 + 1)(5 - 2) = 18 (Right) For w = 7, (7 + 1)(7 - 2) = 40 (Not in option) For w = 9, (9 + 1)(9 - 2) = 70 (Not in option) So you are left with w = 5 and the product possible is : 18...

OpenStudy (karatechopper):

saif....2k+1=2001

OpenStudy (anonymous):

providing a formula for all numbers in that way w=2k+1 (w+1)(w-2)=w^2-w-2=(2k+1)^2-(2k+1)-2=2(2k^2+k-1) k w 2(2k^2+k-1) 0 1 -2 1 3 4 2 5 18 <--- 3 7 40 ...

OpenStudy (asnaseer):

another way of solving this: since w is odd you can also write it as 2k - 1 (I use minus 1 here instead of plus 1 to take advantage of what the question says "1 more than w..." which will then get rid of this -1). so, we have: w = 2k - 1 for k=1,2,... (w+1)(w-2) = 2k(2k - 3) => product is even. so lets divide this and all the given options by 2 to get k(2k-3) which means we need a number that has these two as factors: k(2k - 3) = 0 [k=0 is not valid --- reject] = 5 = 1 x 5 [k=1 => 2k-3=-1 --- reject] = 9 = 3 x 3 [k=3 => 2k-3=3 --- possible] <<<--- answer = 14 = 2 x 7 [k=2 => 2k-3=1 --- reject] = 27 = 3 x 9 [k=3 => 2k-3=3 --- reject] so solution is when k=3, which gives a product of 18 (2 x 9)

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