Arithmetic Sequence Formula: To find the number of terms in an arithmetic sequence, we can use the formula for the nth term of an arithmetic sequence, which is an=a1+(n−1)d, where an is the nth term, a1 is the first term, d is the common difference, and n is the number of terms.
Identify First Term: First, we identify the first term a1 of the sequence, which is 3.
Find Common Difference: Next, we identify the common difference d of the sequence. The difference between consecutive terms is 7−3=4.
Given Last Term: We are given the last term of the sequence an, which is 99.
Set Up Equation: Now we can set up the equation 99=3+(n−1)4 to solve for n.
Simplify Equation: Simplify the equation: 99=3+4n−4.
Combine Like Terms: Combine like terms: 99=4n−1.
Isolate Term with n: Add 1 to both sides to isolate the term with n: 99+1=4n.
Solve for n: Simplify the equation: 100=4n.
Calculate Value of n: Divide both sides by 4 to solve for n: 100÷4=n.
Calculate Value of n: Divide both sides by 4 to solve for n: 100÷4=n.Calculate the value of n: 25=n.
More problems from Find the sum of an arithmetic series