Jane had 275 stickers, which she gave to her friends. each friend got five more stickers than the friend before. if the first friend got 5 stickers, how many friends got stickers from jane?

10 friends.

Step-by-step explanation:

Givens

Sum = 275

a1 = 5

d = 5

n = ?

Formula

Sum = (  (2*a1) + (n - 1)*d) * n / 2   Substitute the knows.

Solution

Sum = ( 2 * 5 + (n - 1)*5 ) * n/2      Combine on the right

275 = (10 + (n - 1)5 ) n/2                Multiply by 2 and remove the brackets.

550 = (10 + 5n - 5) * n                  Combine

550 = (5 + 5n ) * n                        Remove the brackets

550 = 5n + 5n^2                          Subtract 550 from both sides.

5n^2 + 5n - 550 = 0                     Divide by 5 (all terms are divisible by 5)

n^2 + n - 110 = 0                           Factor  

(n + 11)(n - 10) = 0

The only root that has any meaning is n - 10 = 0

n + 11 means Jane has - 11 friends. That has no meaning at all.

n - 10 = 0

n = 10

She had 10 friends who got stickers.

i belive those are the ones that are under 90 degreese.