Without a calculator, how fast can you answer this CSAT practice question?

The Union Public Service Commission has said that June 16 will be the date of the UPSC CSE preliminary test in 2024. Candidates are working through practice exams, reviewing the curriculum, and examining the top scorers from prior years’ answer sheets in advance of the test. A CSAT question that may stump you has been making the rounds on social media as applicants get ready for the forthcoming test.

UPSC Notes shared the question along with the comment, “CSAT practice question.”

“What is the remainder when 3 raised to the power of 2019 is divided by 10?” reads one of the four possible answers to the inquiry. (A) 1, (B) 3, (C) 7, and (D) 9 are these.

On April 21, the brainteaser was released. Since then, it has had over 1.1 million views, and the count continues. Many even shared their opinions in the post’s comments section.

Simple. After each power of three, the remainders are repeated. In other words, 3^1 provides 3 3^2 produces 9, which then leads to 7 1 and so on. Thus, the remainder of 3^2020 or (3^4)^505 is 1. Because 7 appears before 1 in the pattern, 3^2019 should have 7 as the remainder, someone wrote.

One more person said, “7 is the right response.”

The last three-nth digit will be 3,9,7,1,3,9,7,1,3,9,7,1. Are you seeing a trend? You probably do. It’s merely 3971 times repeated repeatedly. One person said, “Three multiples of four will end in one. Three 2016s will end in one. The year 2017 will end in three. Three 2018 will end in nine. Three 2019 will end in seven (Option C).”