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Question Of The week: Why Do Old People Fall Ill?

(0)
April 03, 2009

Ever wondered why nitrogen in the liquefied form is used in medical applications? Or why your grandmother often falls ill?


Well, these were some of the questions asked by Topper readers to our panel of experts.


This week we feature four questions asked by Class X students, along with the answers!
 

 


Subject
: Mathematics


Q.
Show that one and only one of p, p+2 or p+4 is divisible by 3.

 

 

Posted by: SITHARA

 

 

A. Suppose p is divisible by 3 then p=3q (say) where q is some non negative integer.


The next multiple of 3 will be only p+3,p+6 etc( multiples of 3 will occur only after a     gap pf 3)

So, if p is a multiple of 3 then p+2 and p+4 can't be multiples of 3


Next if p+2 is a multiple of 3 then p+2= 3r(say)

So, the multiple of 3 before p+2 must be (p+2)-3 and the next mutiple after p+2 will be (p+2)+3 ie  p-1 and p+5 respectively. So if p+2 is a multiple of 3 then por p+4 can't be multiples of 3.


By a similar logic, we can show that if p+4 is a multiple of 3 then p or p+2 can't be multiples of 3.

This explains the answer.

 

 

 ****

 

 

 

Subject: Chemistry

 

Q. Give reason why nitrogen in the liquefied form finds utility in medical applications such as preserving biological sample!

 

Posted by: Gpriya

 

A. At atmospheric pressure, liquid nitrogen boils at 77 K ('196 °C; '321 °F) and is a cryogenic fluid, thus finding utility in the medical applications like cryopreservation of blood, reproductive cells (sperm and egg), and other biological samples and materials.