m4maths
Maths Puzzle
7, 15, 25, 39, 61, ?
Options 1) 77
2) 79
3) 81
4) 83
5) 87
6) 91
7) 93
8) 99
9) 107
10) none of these
Read Solution (Total 9)
-
- Let the next number be ‘T’
Now let’s take the differences of the consecutive terms of the given sequence:
15 – 7 = 8;
25 – 15 =10;
39 – 25 =14;
61 – 39 = 22;
T – 61 = D; (Let)
Now if we observe the sequence of the differences : 8 , 10 , 14 , 22 ,D,….
We can clearly observe that the differences of consecutive terms are : 2 ,4,8,(D – 22 )….
Where 2=2^1;
4=2^2;
8=2^3;
Therefore 4th term will obviously be [(2^4)=16]; So, (D – 22)=16; => D=38;
Therefore, T= 61+D =61+38=99;
So,The next number will be 99.
The correct answer is OPTION 8.) 99
- 12 years agoHelpfull: Yes(22) No(1)
- 99(ans)
first series contain sum of 7
7,25,61
2+5=7
6+1=7
2nd series contain difference of 6
15,39,?
1+5=6
3+9=12
so choose the option for that sum of digit contain 18
so 99 contain 9+9=18
so 99 is ans
- 12 years agoHelpfull: Yes(9) No(13)
- 7 15 25 39 61
Difference betwn 8 10 14 22
again difference 2 4 8
now 16
22+16=38
so 61+38=99 - 12 years agoHelpfull: Yes(4) No(0)
- 1st term is 7, 2nd term 7+8=15, 3rd term 15+10=25, 4th term 25+14=39,
5th term 39+22=61, 6th term 61+38=99, 7th term 99+70=169
therefore, the answer to this puzzle is 99. - 12 years agoHelpfull: Yes(3) No(1)
- 7, (7+8), (15+8+2^1), (25+8+2^1+2^2), (39+8+2^1+2^2+2^3),(61+8+2^1+2^2+2^3+2^4) so ans is 99
- 12 years agoHelpfull: Yes(2) No(7)
- first series 7,25,61
second series 15,39,x
difference in first series gets multiplied by 2
25-7=18,61-25=36;
so
39-15=24
x-39=48
x=87 - 12 years agoHelpfull: Yes(1) No(12)
- answer:99 the difference is 7-15=8 15-25=10 25-39=14 39-61=22 then next difference is 38.so 61+38=99
- 12 years agoHelpfull: Yes(1) No(0)
- answer is 99
7,1+5=6,2+5=7,3+9=12,6+1=7,9+9=18
7,6,7,12,7,18
so alternative odd position are having 7
alternative even position are having multiples of 6 so 9+9=18
answer is 99
- 12 years agoHelpfull: Yes(0) No(7)
- Ans 8) 99
because every next number= 2*previous number-constant number
this constant number is started with -1 and for every next time 6 is added every time
hence
7*2-(-1)=15
15*2-(5)=25
25*2-(11)=39
39*2-(17)=61
61*2-(23)=99
hence sequence is 7,15,25,39,61,99 - 12 years agoHelpfull: Yes(0) No(0)
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