Question

15,31,35,39,75,79,?.

Answer 1

Step-by-step explanation:

Given series 15,31,35,39,75,79,

It can be written as three groups like

15,31 / 35,39 / 75,79 /

The first numbers in the groups are 15,35,75

35-15=20

31-15=20=20×1

75-35=40=20×2

135-75=60=20×3....like this

and second numbers in the groups

31,39,79

39-31=8

79-39=40=8×5

x-79=40×5=200

=>x=200+79

=>x=279

279-79=200=40×5

The series

15,31,35,39,75,79,135,279,...