Latest TCS Aptitude Question SOLUTION: 7^1+7^2+7^3+...........+7^2015 find out how many numbers present which unit place contain 3 ?

• Placement Papers
• /
• TCS
• /
• Numerical Ability
• /
• Permutation and Combination

TCS Question Papers: TCS Interview Experience(90) TCS Company Profile

(#M40117746) TCS Numerical Ability question Keep an EYE

7^1+7^2+7^3+...........+7^2015 find out how many numbers present which unit place contain 3 ?

Asked In TCS saroj kumar behera (9 years ago)

Solved Pawan Read Solution (6)

Is this Puzzle helpful?   (10)   (2) Submit Your Solution Permutation and Combination

Read Solution (6) :

Pawan  (9 years ago) Best Solution

7^3,7^7,7^11,7^15,7^19.........7^2015 contains last digit=3.
Now,we see
3,7,11,15....2015 are in AP
tn=a+(n-1)d
2015=3+(n-1)4
2015=3+4n-4
4n=2016
n=504
Ans=504.

Is this solution Helpfull? Yes (20) | No (5)  

vinya  (9 years ago)

ans 54
explanation:
cyclic pattern of 7 is 7, 9, 3, 1 i.e., 4 is cyclic pattern number of 7
7^1 = 7
7^2 = 4(9)
7^3 = 34(3)
7^4 = 240(1)
pattern repeats
quotnt(2015/4)= 53 and remainder is 3 ie 7^2015 contains 3 in units digit
so 54 numbers contain 3 in their units place

Is this solution Helpfull? Yes (8) | No (7)  

nisha yadav  (9 years ago)

The number of 11 letter words formed by using English alphabets if all vowels are used such that no two vowels are adjacent to each other is:
a. 5! * 20! / 15!
b. 5! * 21! / 15!
c. 21! / 10!
d. 21! / 15!



20 feb tcs

Is this solution Helpfull? Yes (6) | No (3)  

dipanjan ganguly  (8 years ago)

Vinaya, Please learn how to divide...:D
and Pawan this is not the way of solving it..
Unit digit theorem is enough to explain the answer..
2015/4 =503 (according to cyclic rule of power 7 has a cycle of 4)
2015%4=3 so the last 3 will be 7,9,3...
so we can conclude, (503+1)= 504...:)

Is this solution Helpfull? Yes (4) | No (1)  

Sakshi Agarwal  (8 years ago)

2015=4k+3; k=503
3=4k+3; k=0
Therefore , total nos with last digit 3 = 504

Is this solution Helpfull? Yes (2) | No (1)  

Nayana g biradar  (8 years ago)

7^1=7
7^2=49
7^3=343
7^4=2401
so for every 4 terms we get one term with 3 in its unit digit
so there are total of
2015/4 we will get 503.6 as answer so answer is 504

Is this solution Helpfull? Yes (1) | No (1)  

Please Login to Read Solution.