Question

Amir is starting a stamp collection. After 3 weeks he has collected 35 different stamps, and after 9 weeks he has collected 105 different stamps. If Amir keeps collecting stamps at this same rate, how many stamps will he have after 15 weeks?

Answer 1

Answer:

if 3 wks = 35 stamps

9 wks = 105 stamps

then fifteen weeks = 35 × 15

= 525 different stamps

Answer 2

Answer:

He will have 175 stamps after 15 weeks

Step-by-step explanation:

After 3 weeks he has collected 35 different stamps

(3,35)

After 9 weeks he has collected 105 different stamps

(9,105)

We are given that supposed to find how many stamps will he have after 15 weeks

Formula : $y-y_1=\frac{y_2-y_1}{x_2-x_1}(x-x_1)$

$(x_1,y_1)=(3,35)\\(x_2,y_2)=(9,105)$

Substitute the values in the formula :

$y-35=\frac{105-35}{9-3}(x-3)$

$y-35=\frac{35}{3}(x-3)$

$3y-105=35x-105$

$y=\frac{35}{3}x$

y is the no. of stamps

x is the no. of weeks

Substitute x =15

$y=\frac{35}{3}(15)$

$y=175$

Hence he will have 175 stamps after 15 weeks