Question

15 21 39 77 143 (?)
(1) 243
(2) 240
(3) 253
(4) 245

Answer 1

Its (4)245

The pattern is 
15     21     39        77        143            ?
    +6    +18      +38     +66        +102
        +12      +20     +28      +36
               +8        +8        +8        +8 
now 8+36= 102
        102+143= 245

Answer 2

Answer:

4

Step-by-step explanation:

Let we find the common difference of the numbers.

15, 21, 39, 77, 143 = 6, 18, 38, 66

6, 18, 38, 66 = 12, 20, 28

12, 20, 28 = 8, 8

8, 8 = 0

Then, 8 + 28 + 66 = 102

To find next number of 143 so, 143 + 102 = 245.

Therefore, the series is 15, 21, 39, 77, 143, 245.

#SPJ3