# Few questions from JEE Main online exam, 9th April 2013

There are some questions from JEE Main online exam that was held on 9th April 2013. These questions are provided by users on 100Marks.
If you remember any other question, please mail them to us at info@100marks.in.
1. An engine is getting up a hill. It is at 0.9km then the driver sounds a Horn and its echo is heard by him after 5 sec . It the sound travels at a speed 330m/s . Then what is the speed of the engine ?
2. ( 1 / 1 ) + ( 1 / 1+2 ) + ( 1 / 1+2+3 ) ….. upto 10 .. the sum would be
Option A ,. 20 / 11 B,. 18 / 11 C,. 16 / 9 D, 22 / 13
3. If A B C are the sides of a triangle then Determinant a b c , b c a , c a b would be … ( its in the determinant form 3 x 3 matrix ) would be
options 1, Positive 2, Negative 3, Non- Negative 4, Non-Positive
4. Here’s one x^2/4c^2 + y^2/c^2 = 1 is an ellipse and there is a circle x^2 +y^2=9a^2 …. Find the condition in terms of a and c such that they intersect in 4 points..

• mastercool8695

• TavleenKaur

1.let v be the velocity of engine. so relative speed of sound is 330-v whereas the distance it has to cover is 1.8km or 1800m (900m in going and 900m in returning) .time taken is 5 sec. so 1800=(330-v).5

• MangeshKokare

what is  the method for 2nd sum

• AppunniMohanan

@MangeshKokare 2[ (1 – 1/2 )+ (1/2 – 1/3) + ……. ) upto ten terms so last term will be  (1/10 – 1/11).  All terms cancel out except first and  last so  answer = 2( 1 – 1/11 )= 20/11.

• AppunniMohanan

HCl + 3-phenylpropene gives  ?
ans : 1-choro-1-phenylpropane

• SahilSinghal

help me with que no. 2