GATE | GATE-CS-2017 (Set 2) | Question 8



X is 30 digit number starting with 4 followed 7. Then number X3 will have
(A) 90 digits
(B) 91 digits
(C) 92 digits
(D) 93 digits


Answer: (A)

Explanation:

X = 4777....(till 30 digits)

or X = 4.7777⋯ ∗ 1029

X29 = (4.777⋯∗1029 )
  = (4.777…)∗ 10 87

So, (X3 ) requires 3 + 87 = 90 digits. 

Therefore, option A

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