Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 90)
90.
What is the unit digit in(795 - 358)?
Answer: Option
Explanation:
Unit digit in 795 = Unit digit in [(74)23 x 73]
= Unit digit in [(Unit digit in(2401))23 x (343)]
= Unit digit in (123 x 343)
= Unit digit in (343)
= 3
Unit digit in 358 = Unit digit in [(34)14 x 32]
= Unit digit in [Unit digit in (81)14 x 32]
= Unit digit in [(1)14 x 32]
= Unit digit in (1 x 9)
= Unit digit in (9)
= 9
Unit digit in (795 - 358) = Unit digit in (343 - 9) = Unit digit in (334) = 4.
So, Option B is the answer.
Discussion:
36 comments Page 3 of 4.
J GOPINATH said:
9 years ago
Here as per the logic, it's if subtracted it will be 6 but with the negative symbol so you have borrow 10 from the previous place i. e, ten's place which makes the 3 to be 13 and hence 13-9=4 which the correct answer choice.
(1)
Bidyut ghosh said:
9 years ago
Thank you for explaining the solution.
Madhuri said:
9 years ago
(7^95 - 3^58) = 7 - 3 = 4.
Ali N said:
9 years ago
@Cradlerian.
Thanks for your solution.
Thanks for your solution.
Zahin said:
10 years ago
Or the simplest way would be like this:
As the power of 7 is odd. Do an odd power multiplication.
Like 7^3 and the power of 3 is even. So do an even power multiplication.
Like 3^2 subtract them and then you will get the units digit.
For example: 7^3-3^2=334. Here units digit is 4. So its that easy.
As the power of 7 is odd. Do an odd power multiplication.
Like 7^3 and the power of 3 is even. So do an even power multiplication.
Like 3^2 subtract them and then you will get the units digit.
For example: 7^3-3^2=334. Here units digit is 4. So its that easy.
Cradlerian said:
10 years ago
7^95 = 95/4 = remainder 3.
3^58 = 58/4 = remainder 2.
So, 7^3 = 343 & 3^2 = 9.
Since we have (7^95-3^58),
Therefore, 343-9 = 334.
Unit digit is = 4.
3^58 = 58/4 = remainder 2.
So, 7^3 = 343 & 3^2 = 9.
Since we have (7^95-3^58),
Therefore, 343-9 = 334.
Unit digit is = 4.
Jot said:
1 decade ago
My answer is 6. But how is it 4? Please elaborate clearly.
(1)
Naveen said:
1 decade ago
Unit digit should not show in negative digits. So actually total digit in 7^95 is 343.43-9=34.
So 4 is the correct answer.
So 4 is the correct answer.
Prasanna Karthik said:
1 decade ago
Hi guys,
Here the concept is ultimately to make 1 as base so that 1 power anything will be one only.
7^95 = (7^2)^47 X 7 = 9^47 X 7 = ((9^2)23) X 7 X 9 = 1^23 X 63 = 63 (Remember here I am only considering nit digits).
Same as calculate for 3^58 it will be 9, so the answer is 63-9 = 54 = 4 (Unit digit).
Here the concept is ultimately to make 1 as base so that 1 power anything will be one only.
7^95 = (7^2)^47 X 7 = 9^47 X 7 = ((9^2)23) X 7 X 9 = 1^23 X 63 = 63 (Remember here I am only considering nit digits).
Same as calculate for 3^58 it will be 9, so the answer is 63-9 = 54 = 4 (Unit digit).
Kunvar said:
1 decade ago
I want to correct you. We are not finding the absolute value of the question. 3-9 = 6 is not the answer as it is -6 and you people don't know the concept of negative remainders and modulo. So the answer 4 is absolutely right.
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