What should come in place of question mark (?) in the given number series ?
let the missing number be x
15 - 13 = 2
20 - 15 = 5
37 - 20 = 17
102 - 37 = 65
y - 102 = z
Now, take difference of differences
5-2 = 3
17 -5 =12
65- 17 = 48
Here we can see 12 = 3×4,48=12×4
z-65 = 48 ×4
z = 257
Hence y = 102 + 257 = 359
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