Aptitude - Numbers - Discussion
Discussion Forum : Numbers - General Questions (Q.No. 121)
121.
What is the unit digit in the product (365 x 659 x 771)?
Answer: Option
Explanation:
Unit digit in 34 = 1 
Unit digit in (34)16 = 1
Unit digit in 365 = Unit digit in [ (34)16 x 3 ] = (1 x 3) = 3
Unit digit in 659 = 6
Unit digit in 74 Unit digit in (74)17 is 1.
Unit digit in 771 = Unit digit in [(74)17 x 73] = (1 x 3) = 3
Required digit = Unit digit in (3 x 6 x 3) = 4.
Discussion:
39 comments Page 3 of 4.
Amar said:
8 years ago
Why we take 3 to the power 4? Please explain.
Hrushi said:
8 years ago
Thanks @Jyothi.
Gokul said:
8 years ago
How 6^59 is only 6?
Soundarya said:
8 years ago
Please explain 6^59=6.
Arijit said:
8 years ago
3^65 * 6^59 * 7^71.
= ? * 6 * ? // If the unit digit of base is [0,1,5,6] then answer will be same
= 3^1 * 6 * 7^3 // If the unit digit of base is other than [0,1,5,6] then divide the power with 4 and remainders will be one of these [0,1,2,3], take the remainder as the power of unit digit of the base.
=3 * 6 * 3 // unit digit of 7^3 will be [7*7*7 , take 49*7 and calculate only unit digit which is 9*7 = 63 and unit digit is 3]
=4 // [18 * 3 here calculate only unit digit which is 8*3 = 24 , and answer will be 4]
= ? * 6 * ? // If the unit digit of base is [0,1,5,6] then answer will be same
= 3^1 * 6 * 7^3 // If the unit digit of base is other than [0,1,5,6] then divide the power with 4 and remainders will be one of these [0,1,2,3], take the remainder as the power of unit digit of the base.
=3 * 6 * 3 // unit digit of 7^3 will be [7*7*7 , take 49*7 and calculate only unit digit which is 9*7 = 63 and unit digit is 3]
=4 // [18 * 3 here calculate only unit digit which is 8*3 = 24 , and answer will be 4]
Madhusudhan ar said:
8 years ago
@Jyothi.
Thank you so much for your explanation.
Thank you so much for your explanation.
Madhusudhan said:
8 years ago
Anyone please explain (7^95-3^58).
Aung aung said:
7 years ago
I don't understand 6^59=6, please explain me.
Ashwini said:
7 years ago
How 7^4 ^17? please explain me clearly.
Havish said:
7 years ago
Unit digit of 7^71wxplantion:
7^7=49 in dis unit digit is 9
Then 7 multiplied by 49 leaves unit digit as 3,
Then 7 multiplied again gives 1,
Again 7 multiplied gives 7.
Repaet d order like : 9,3,1,7,9,3,1,7,9,3,1,7
In the order, 11th place gives 1 which would be identical to 7^71.
Ex: lf it's 7^ 72 then the unit place would be 7.
7^7=49 in dis unit digit is 9
Then 7 multiplied by 49 leaves unit digit as 3,
Then 7 multiplied again gives 1,
Again 7 multiplied gives 7.
Repaet d order like : 9,3,1,7,9,3,1,7,9,3,1,7
In the order, 11th place gives 1 which would be identical to 7^71.
Ex: lf it's 7^ 72 then the unit place would be 7.
(1)
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