7, 15, 25, 39, 61, ?

jyotish r   11 years AGO

taking difference of adjacent terms ,
(15-7),(25-15),(39-25),(61-39) ie,
8,10,14,22
again taking differences,
(10-8),(14-10),(22-14)
ie,
2,4,8.this is the series of powers of two.

so the next 2nd level difference is 2^4=16

so, the next first level difference is 22+16=38

so, the next term in given sequence is 61+38=99 is the answer

Like? Yes (11) | No (3)  

sathyasagar   11 years AGO

7+8=15
15+10=25 (here 10 = 8 + 2^1)
25+14=39 (here 14 = 10 + 2^2)
39+22=61 (here 22 = 14 + 2^3)
61+38=99 (here 38 = 22 + 2^4)

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nayana s   11 years AGO

15-7=8
25-15=10(10-8=2)
39-25=14(14-10=4)
61-39=22;(22-14=8)
then,the subtraction of next number ll be 38;(38-22=16),
so,61+38=99...

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PARAG KAMRA   11 years AGO

15-7=8,25-15=10,39-25=14,61-39=22
so diff is 8,10,14,22
so in this diff of power of 2
2,4,,8
so next diff will be of 16 so next diff will be 38
8,10,14,22,38
so next 61+38=99(ans)

another formula take two series 7,25,61
7,2+5=7,6+1=7
2nd series 15,93,?
1+5=6,9+3=12
so next will be sum of 18 so 99 will come(ans)

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Madhu   11 years AGO

7,1+5=6,2+5=7,3+9=12,6+1=7,9+9=18
7,6,7,12,7,18

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Ashutosh   11 years AGO

7 15 25 39 61 99
8 10 14 22 38
2 4 8 16

It is increasing in the second difference in the series 2 to the power 1,then 2 to the power 2, ...

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Ashutosh   11 years AGO

7 15 25 39 61 99
8 10 14 22 38
2 4 8 16

It is increasing in the second difference in the series 2 to the power 1,then 2 to the power 2, ...

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ajitha   11 years AGO

ans:99


7,15,25,39,61,99(61+38)
\ /\ /\ /\ / ^
|
difference between two sequence numbers: -8-10-14-22 38(22+16)
\ / \ /\ / |

similarly the difference between two num: 2 4 8 ^
|
so the sequence should be (powers of two): 2 4 8 16

Like? Yes (2) | No (1)  

phani   11 years AGO

the first differences are 8,10,14,22,......
the second differences are 2,4,8,..so it is 16
then first differnce is 22+16=38
number=61+38=99

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neeraj kumar   11 years AGO

7+8=15,15+10=25,25+14=39,39+22=61,61+38=99
series is 8,10,14,22,38
since difference of both are 2,4,8,16

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ajay burnwal   11 years AGO

7+8=15,15+10=25,25+14=39,39+22=61,61+38=99
series is 8,10,14,22,38
since difference of both are 2,4,8,16

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jomon v j   11 years AGO

answer 99

15-7 =8
25-15=10
39-25=14
61-39 =22

difference between numbers is power of 2

10-8=2
14-10=4
22-14=8
so next we have to add 16 with 22 =38

next number is 61+38=99

61-39=22

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Shiv Kumar   11 years AGO

First Difference is increasing by multiple of 2

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Pranaya   11 years AGO

15-7=8, 25-15=10, 39-25=14, 61-39=22
series form 8,10,14,22 now again difference between them we get 2,4,8, then next will be 2^4=16,
add 16 to 22 we get 16+22=38 then
add 38+61=99
next number is 99.

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Md Zahid Akhtar Molla   11 years AGO

15-7=8
25-15=10
39-25=14
61-39=22
Again 10-8=2
14-10=4=2^2
22-14=8=2^3
so next difference will 2^4=16
now 22+16=38
and 61+38=99
So the ans will be 99.

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md irshad ali   11 years AGO

(15-7)=8
(25-15)=10
(39-25)=14
(61-39)=22
AGAIN
(10-8)=2
(14-10)=4
(22-14)=8..I.E.2^N
HENCE NEXT TERM=61+22+(2*4)=

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Akanksha Narula   11 years AGO

7,15,25,39,61,?
if the 2nd term-1st term
the series cms
+8,+10,+14,+22,+?
again a series
+2,+4,+8,+16
so the next term wil be 22+16=38 for the 2nd series.
and 61+38=99 ..is the ans

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SDeep Bhattacharya   11 years AGO

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

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RIMAN   11 years AGO

(15-7) = 8
(25-15)= 10 ; (10-8)= 2
(39-25)= 14 ; (14-10)=4
(61-39)= 22 ; (22-14)=8 so next diff. is 16
now (22+16)=38
and oue required ans is (61+38)=99

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RAHUL YADAV   11 years AGO

the difference in the series are 8,10,14,22.
and the difference between no in this is 2,4,8 which is a 2^1=2; 2^2=4; 2^3=8; 2^4=16.
therefore add 22+16=38.
and now add 61+38=99

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Jamil Ahmed   11 years AGO

The difference of two consecutive numbers goes on increasing by 2,4,8,16. So the differences are 8,10,14,22 and then 38.
Hence, the answer is 61+38=99

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susmit   11 years AGO

difference in given nos. is 8,10,14,22
difference in these nos. is 2,4,8 i.e. 2^1,2^2,2^3
so the nest difference is 2^4=16
22+16=38
hence the answer is 61+38=99
option no.8

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vivek chauhan   11 years AGO

7+8=15
15+10=25
25+14=39
39+22=61
61+38=99

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