Respuesta :
Answer:
9 days
Step-by-step explanation:
Since the secret spread at a geometric rate we will use the geometric progression formulae
ar^n-1
First term = a= 5
common ratio is 2
For the nth term
5*2^n-1 = 1280 divide both sides of the equation with 5
2^n-1 = 256
2^n-1= 2^8
n-1 =8
n = 8+1
n=9
All the children will know the secret in 9 days
Alternatively
2nd day= 5*2^2-1
5*2^1=
5*2= 10
3rd day = 20
4th day= 40
5th day= 80
6th day = 160
7th day = 320
8th day =640
9th day =1280 children
