Try this one !!!

Ques) If Ck is a circle of eqn x2 + y2 = k2 ; k belongs to N, a point moves k units on Ck in anticlockwise direction then goes to C k+1 and so on. If point starts frm (1,0) and Ist time crosses the +ve x-axis on circle Cn , then the value of n equals to
(a) 7 (b) 6 (c) 5 (d) 13

the ques isn't clear to me

7 Answers

1
Grandmaster ·

its means the point moves each time substending an angle of 1 rad..the answer should be 7

1
Grandmaster ·

sorry it should be 6

11
Tush Watts ·

nops ans given is (a) 7 [2]

106
Asish Mahapatra ·

Ques) If Ck is a circle of eqn x2 + y2 = k2 ; k belongs to N, a point moves k units on Ck in anticlockwise direction then goes to C k+1 and so on. If point starts frm (1,0) and Ist time crosses the +ve x-axis on circle Cn , then the value of n equals to
(a) 7 (b) 6 (c) 5 (d) 13

starts from (1,0) goes 1 unit on C1 anticlockwise i.e. covers 1 rad.

Each circle it covers 1 rad.
so, C2 -- > 2rad (end point)
C3 --> 3rad
C4 --> 4rad
.
.
.
C6--> 6rad
C7 --> 7rad

Now 2pi rad = 6.28 rad.

So it will be on the 7th circle when crossing the x-axis.

11
Tush Watts ·

Thanx a lot Asish [1]

24
eureka123 ·

If u r intrested....then see the better version of the ques
http://targetiit.com/iit-jee-forum/posts/iit-jee-next-level-4132.html

11
Tush Watts ·

ok thanx eure

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