Question

You tell two friends about a website they can go to in order to receive coupons to a popular clothing store. the next day, each of them tells 2 more friends, and the next day, each of those friends tells 2 more friends. so the first day, 2 new people know about the coupons; the second day, 4 new people know about the coupons; the third day, 8 new people know about the coupons, etc. how many people find out about the coupons on the ninth day?

Answer 1

Create a table.

Day # New people
-------- -----------------
1 2 = 2¹
2 4 = 2²
3 8 = 2³

By induction, on the n-th day, the number of new people is 2ⁿ.

On the 9-th day, there will be 2⁹ = 512 new people.

Answer: 512

Answer 2

512 people will know about website on ninth day

Explanation:

We are given that You tell two friends about a website they can go to in order to receive coupons to a popular clothing store.

So, on day 1 ,No. of people know about the website =2

On day 2 , each of them tells 2 more friends

Now since each of them tells 2 friends .

So, 2 told no. of friends = 2*2=4

Now on Day 3 , these four friends, each of them told 2 more friends

So, total no. of friends told about the website by these four friends = 2+2+2+2=8 friends

SO, if we consider the sequence no. of friends know about the website on days

Day 1 :
`2^1=2`

Day 2 :
`2^2=4`

Day 3:
`2^3=8`

So, the general form of sequence becomes :
`2^n`

Where n denotes the no. of day

So, on Day 9 the no. of peolple finds about website :

`2^9`

`512`

Hence 512 people will know about website on ninth day