Hi SajjadAhmad,
Based on the answers choices (and the correct answer), the "intent" of this question is that that Z = (10^N) - 4. We're also told that the sum of the DIGITS of Z is 186. We're asked for the value of N.
Consider the following examples...
IF....
N = 1, then Z = 10 - 4 = 6 and the sum of the digits is 6
N = 2, then Z = 100 - 4 = 96 and the sum of the digits is 15
N = 3, then Z = 1000 - 4 = 996 and the sum of the digits is 24
Notice that when N increases by 1, the sum of the digits of Z increases by 9. To answer this question, we just have to determine how many additional "9s" we have to add to get the sum of the digits up to 186.
Since N = 1 led to a sum of 6, we need twenty 9s to get the sum up to 186. Thus, N would have to be 1 + 20 = 21
Final Answer:
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Rich
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