Question

Find unit digit of 141+241+341+…….9941?

B 1 Correct Answer Incorrect Answer
C 2 Correct Answer Incorrect Answer
D 6 Correct Answer Incorrect Answer

Solution

141+241+341+…….9941 When 41 is divided by 4 remainder is 1. 11+21+31+41……………991 That means 1+2+3+4….99, which is sum of natural number from 1 to 99. Apply sum of natural number formulae n(n+1)/2 N=99 put and solve we gives unit digit 0. Option1.

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