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1,7,8,49,50,56,57,343,344,350,351,392,393,399,400
The above sequence contains sum of distinct power of 7 in increasing order(7^0,7^1,7^1+7^0,7^2 etc.) What is value of term number 38 ?
Read Solution (Total 14)
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- 2nd term is 7^1
4th term is 7^2
8th term is 7^3
so 16th term will be 7^4 and 32nd=7^5
now as we see 3rd term=7+1
5th term=49+1
6th term=49+7
7th term=49+8
now,9th term=343+1
10th=343+7
11th=343+8
12th=343+49 and so on..
so, 33rd term=(7^5)+1=16808
34th=16807+7
35th=16807+8
38th=16807+56=16863 (ans) - 12 years agoHelpfull: Yes(26) No(17)
- akshay your soloution is wrong..clear your basics dont mislead..
in these type of questions there is a trick
as shown is series it is like
7^0
7^1
7^0+7^1
7^2
7^0+7^2
7^1+7^2
.....
hence last term in power five will be
7^5+7^4+7^3+7^2+7^1+7^0 this is first method
now second method is trick based that is we want 38 term directly solve like this
so first number is 3 and second is 8 so gap is 8-3=5 when we calculate this polynomial hence ans is 7^3+7^5=17150..
- 12 years agoHelpfull: Yes(19) No(19)
- @akshay shut up and mind your language..
- 12 years agoHelpfull: Yes(6) No(7)
- @swati first see your language then tell me anything...so you shut up..
- 12 years agoHelpfull: Yes(6) No(6)
- It is very simple. Convert the number to binary. For example 5 = 101 in binary. So, the 5th term is 7^2 + 7^0 = 50 ignoring zeros of binary numbers. Another example 10 = 1010 in binary. So, the 10th term is 7^3 + 7^1 = 350. Now, 38 = 100110 in binary. So, 38th term = 7^5 + 7^2 + 7^1 = 16863.
- 12 years agoHelpfull: Yes(6) No(0)
- clearly we have pattern here.... the power term positions follow like
for 38th value split it in the powers of 2 like
38 = 32+6
32+4+2
then write as 2^5+2^2+2^0
then just replace the 2 base with 7 number given that leads us to
=7^5+7^2+7^0
=16807+49+1
=16857
now we can do this method for any value series
- 12 years agoHelpfull: Yes(5) No(1)
- @ SWATI SINGH
give your answer if u want dont judge anyone's answer...
now i have given it with logic.. - 12 years agoHelpfull: Yes(3) No(7)
- answer is 7^5+7^2+7^1=16863
- 12 years agoHelpfull: Yes(3) No(0)
- akshay jain can u please explain how??
- 12 years agoHelpfull: Yes(2) No(3)
- ans -16863
- 12 years agoHelpfull: Yes(2) No(2)
- ans is=16978
- 12 years agoHelpfull: Yes(1) No(9)
- the 38th term will be 7^3+7^7=823886
- 12 years agoHelpfull: Yes(0) No(0)
- please send it today at sobhandutta@gmail.com
- 11 years agoHelpfull: Yes(0) No(0)
- In PRASANTH G KRISHNA solution I made the correction.
clearly we have pattern here.... the power term positions follow like
for 38th value split it in the powers of 2 like
38 = 32+6
32+4+2
then write as 2^5+2^2+2^1
then just replace the 2 base with 7 number given that leads us to
=7^5+7^2+7^1
=16807+49+7
=16863
now we can do this method for any value series - 5 years agoHelpfull: Yes(0) No(0)
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