GATE Questions

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Ans. 
17 = 2 x 6 + 5
89 = 17 x 5 + 4
359 = 89 x 4 + 3
1079 = 359 x 3 + 2
? = 1079 x 2 + 1, i.e. ? = 2159

The given series follows a pattern of +19, x19, +17, x17, +15, x15,...

Here the number which is to be replaced in ? is

41310+15=41325.

From the given data,

Let the two gits of a number be x & y

A) x + y = 15

B) x2 - y2 = 45

(x+y) (x - y) = 45

C) x - y = 3

From any 2 of the given 3 statements, we can find that 2 digit number as 

2x = 18 => x = 9

=> y = 6

Hence, 2 digit number is 96.

Any one pair of A and B, B and C or C and A is sufficient to find.

Since each ring consists of six different letters, the total number of attempts possible with the three rings is = 6 x 6 x 6 = 216. Of these attempts, one of them is a successful attempt.

Maximum number of unsuccessful attempts = 216 - 1 = 215.

Let Rajeev's present age be  x years.

Rajeev's age after 15 years = (x + 15) years.

Rajeev's age 5 years back = (x - 5) years

Then ATQ, 

x + 15 = 5 (x - 5)

x + 15 = 5x - 25

=> x = 10

Hence, Rajeev's present age = x = 10 years.