Question

question 13 of 25
if the pattern below follows the rule \starting with 10, every consecutive line has a number 1 less than the previous line,\ how many marbles must be in the seventh line?
a. 7
b. 4
c. 6
d. need more information

Explanation:

Step1: Define the sequence rule

This is an arithmetic sequence where first term $a_1 = 10$, common difference $d = -1$. The nth term formula is $a_n = a_1 + (n-1)d$.

Step2: Plug in n=7 for 7th line

Substitute $a_1=10$, $n=7$, $d=-1$ into the formula:
$a_7 = 10 + (7-1)(-1)$

Step3: Calculate the result

Simplify the expression:
$a_7 = 10 - 6 = 4$

Answer:

B. 4