Aptitude - Numbers - Discussion

Discussion Forum : Numbers - General Questions (Q.No. 90)
90.
What is the unit digit in(795 - 358)?
0
4
6
7
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 2 of 4.

Kala said:   1 decade ago
7^3=343 and 3^2=9
difference 343-9
ans 4
How? Please explain every step.
(1)

Jot said:   1 decade ago
My answer is 6. But how is it 4? Please elaborate clearly.
(1)

Ranga said:   6 years ago
Because 6 is an actual difference but negative come to take 10 value.

i.e means 10-6 = 4 is the right answer.
(1)

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)

Pranasish said:   7 years ago
Step1. Find the period of 7=7^0=1.
7^1=7.
7^2=9.
7^3=3.
So the period of 7 is 4.

Divide the power of 7 is 95 by 4 and find the remainder.

So the remainder is 3.so the 3rd unit digit of the period is 3.
step2: Similarly find the period of 3 and find the remainder. this remainder is 2nd, so the 2nd unit digit of the 3 periods is =9.

Step3: The Final ans=(3-9)=4 hints:3 is small as compare 9. So borrow 1 from left digit.

Dipankar Mahanta said:   7 years ago
7^95= 95/4 = remainder 3 = 7^3 = 3 from cyclicity.

3^58= 58/4 = remainder 2 = 3^2 =9 from cyclicity.

NOW, the answer CANNOT be a -ve no, so in order to subtract 9 from 3, we borrow to make it 13 such that= 13-9 = 4 which is a unit digit itself.

Arsalan said:   8 years ago
Hi,

If number^K and k is zero then we take the last value of cycle that is in case of 7 the cycle is of 4 7^1 is 7.

7^2 is 49, 7^3 is 343 and 7^4 ends with 1 and 7^5 ends with 7 so we see the cycle starts again after 4 steps this 7 has a cyclicity of 4 and now if we have number^k and k is divisible by 7 we take 7^4 for unit digit.

Snehasish said:   6 years ago
To all values of n = (x*m-a*m) is divisible by (x- a) thus 7-3 = 4 is the Ans.

Premnath said:   6 years ago
How come we take,
7^95 = 7^92+7^3?

What happens if we take, 7^95 = 7^93 + 7^2, How to solve this? Please tell me.

Jangyaseni Mohanty said:   1 month ago
Agree, the answer is 4.


Post your comments here:

Your comments will be displayed after verification.