Elena wants to have an average of at least 90 on her tests. If she took three tests and earned scores of 94, 92 and 79, what is the lowest score on the fourth test she has to earn
to achieve her goal?
a) 92
b) 88
c) 94
d) 95

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for