Question

Dante is selling donuts outside a huge office building every morning. The first week

he made $25 selling donuts, the second week he made $45 the third week he made
$65! Everyone loved them and they are spreading the word. If this pattern continues
how much money will he be making in week 10?

Answer 1

$205

Explanation:

45 - 25 = 20

65 - 45 = 20

as you can see the common difference between the 3 consecutive numbers 25 , 45 and 65 is a constant (20)

so ,we are in an arithmetic sequence case with :

• first term 25

• common difference r = 20

Let’s label the sequence: Un

then

Un = U1 + (n-1)×r

= 25 + (n-1)×20

= 20n + 5

for n = 10 → U10 = 20(10) + 5 = 200 + 5 = 205