IIT JEE past question AP GP 6

S1, S2.... be squares such that for each n>=1, the length of the side of Sn equals to the length of the diagonal of Sn+1...

If side of S1 is 10 cm, for which of these values of n is the area of Sn less than 1 sq. cm?

2 Answers

62
Lokesh Verma ·

finish this also.. it is easy

106
Asish Mahapatra ·

Let side of S1 = a ... area of S1 = a2
diag of S2 = a ==> side of S2 = a/√2 ... area of S2 = a2/2
diag of S3 = a/√2 ==> side of S3 = a/2 ... area of S3 = a2/4
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Area of Sn = a2/2n-1

now a = 10cm

So, 100/2n-1 < 1
==> 2n-1 > 100
==> n-1 > 7
==> n>8

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