How quickly can you solve this CSAT practice question without using a calculator?

The Union Public Service Commission recently announced that the UPSC CSE prelims exam 2024 will be held on June 16. Ahead of the examination, aspirants are solving mock tests, revising the syllabus and looking at the answer sheets of the previous years’ toppers. As aspirants are prepping for the upcoming exam, a CSAT question has been doing the rounds on social media and may leave you baffled.

Read| Can you solve this aptitude question asked in UPSC CSE Prelims?

The question was posted by UPSC Notes with the caption, “CSAT practice question.”

“If 3 raised to the power 2019 is divided by 10, then what is the remainder?” reads the question, which has four options. These are: (a) 1, (b) 3, (c) 7, and (d) 9.

Take a look at the brain teaser right here:

The brain teaser was shared on April 21. It has since then accumulated over 1.1 lakh views and still counting. Many even took to the comments section of the post to share their thoughts.

Check out how people reacted to this post here:

“Easy. The remainders repeat after every power of 3. That is 3^1 gives 3 3^2 gives 9 Then 7 1 Then 3, 9, 7, 1 and this repeats. So 3^2020 or (3^4)^505 has 1 as remainder. Hence, 3^2019 should have 7 as the remainder because 7 comes before 1 in the pattern,” posted an individual.

Another added, “7 is the correct answer.”

“Last digit of 3^n will be 3,9,7,1,3,9,7,1,3,9,7,1. Do you see a pattern? I bet you do. It is just 3971 repeating over and over again. 3^multiples of 4 will end in 1. 3^2016 will end in 1. 3^2017 will end in 3. 3^2018 will end in 9. 3^2019 will end in 7 (Option C),” expressed a third.