Constraints !

mr. weber drives to a landscape supply center to buy sand and gravel. the center has 6 lb of sand and 13 lb of gravel in stock. mr. weber needs at least 2 lb of sand. the amount of gravel he will buy will be at least twice the amount of sand he will buy.

mr. weber buys 7 lb of gravel. how much sand can he buy?

choose all answers that are correct.

a 2 lb
b 3 lb
c 4 lb
d 5 lb
e 6 lb

, 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