For AI agents: use /llms.txt for the Nakafa content index.
An arithmetic sequence is a sequence of numbers where the difference between consecutive terms is always constant. This difference in an arithmetic sequence is denoted by b b b .
Consider the following number sequence:
4 , 6 , 8 , 10 , . . . 4, 6, 8, 10, ... 4 , 6 , 8 , 10 , ...
In this sequence, we can see that:
The difference between the second and first term: 6 − 4 = 2 6 - 4 = 2 6 − 4 = 2
The difference between the third and second term: 8 − 6 = 2 8 - 6 = 2 8 − 6 = 2
The difference between the fourth and third term: 10 − 8 = 2 10 - 8 = 2 10 − 8 = 2
Since the difference between consecutive terms is always 2 2 2 , this sequence is an arithmetic sequence with common difference b = 2 b = 2 b = 2 .
The common difference (b b b ) in an arithmetic sequence can be calculated by subtracting consecutive terms:
U n U_n U n represents the n n n
th term
U n − 1 U_{n-1} U n − 1 represents the (n − 1 n-1 n − 1
)th term
To determine the n n n th term of an arithmetic sequence, we can use the formula:
U n U_n U n = the n n n
th term
a a a = first term
n n n = term number
b b b = common difference
If we write the first few terms of an arithmetic sequence:
1 1 1 st term: U 1 = a U_1 = a U 1 = a
2 2 2 nd term: U 2 = a + b U_2 = a + b U 2 = a + b
3 3 3 rd term: U 3 = a + 2 b U_3 = a + 2b U 3 = a + 2 b
4 4 4 th term: U 4 = a + 3 b U_4 = a + 3b U 4 = a + 3 b
5 5 5 th term: U 5 = a + 4 b U_5 = a + 4b U 5 = a + 4 b
From this pattern, we can see that the n n n th term is:
Consider the number of seats in a performing arts theater:
Row 1 1 1 has 20 20 20 seats.
Row 2 2 2 has 24 24 24 seats.
Row 3 3 3 has 28 28 28 seats.
Row 4 4 4 has 32 32 32 seats.
Row 5 5 5 has 36 36 36 seats.
To determine the number of seats in a specific row, we need to find the pattern in this data.
Step 1 1 1 : Finding the common difference between rows
Row 2 − row 1 \text{Row }2 - \text{row }1 Row 2 − row 1 : 24 − 20 = 4 24 - 20 = 4 24 − 20 = 4
Row 3 − row 2 \text{Row }3 - \text{row }2 Row 3 − row 2 : 28 − 24 = 4 28 - 24 = 4 28 − 24 = 4
Row 4 − row 3 \text{Row }4 - \text{row }3 Row 4 − row 3 : 32 − 28 = 4 32 - 28 = 4 32 − 28 = 4
Row 5 − row 4 \text{Row }5 - \text{row }4 Row 5 − row 4 : 36 − 32 = 4 36 - 32 = 4 36 − 32 = 4
We can see that the difference between the number of seats in consecutive rows is 4 4 4 . This means the number of seats in this theater forms an arithmetic sequence with:
First term a = 20 a = 20 a = 20
Common difference b = 4 b = 4 b = 4
Step 2 2 2 : Using the formula to find the number of seats in row 15 15 15
Therefore, there are 76 76 76 seats in row 15 15 15 .
Given an arithmetic sequence with the 3 3 3 rd term equal to 9 9 9 and the 6 6 6 th term equal to 18 18 18 . Find the formula for the n n n th term.
To determine the formula for the general term, we need to find the values of the first term ( a ) (a) ( a ) and the common difference ( b ) (b) ( b ) .
We eliminate these equations to find the value of b b b :
After finding b b b , we substitute it into the first equation to find a a a :
With a = 3 a = 3 a = 3 and b = 3 b = 3 b = 3 , we can formulate the n n n th term:
Therefore, the formula for the general term of this sequence is U n = 3 n U_n = 3n U n = 3 n
Rudi saves money in a bank with a constant monthly increase. If in the 5 5 5 th month, he saves Rp 70,000.00 \text{Rp}70{,}000.00 Rp 70 , 000.00 and in the 9 9 9 th month, Rudi saves Rp 90,000.00 \text{Rp}90{,}000.00 Rp 90 , 000.00 .
What is the monthly increase in savings amount?
How much money did Rudi save for the first time?
Rudi's savings form an arithmetic sequence because the monthly increase is constant.
Finding the monthly increase in savings
Eliminating equations 1 1 1 and 2 2 2 :
Therefore, the monthly increase in Rudi's savings is Rp 5,000.00 \text{Rp}5{,}000.00 Rp 5 , 000.00 .
Finding Rudi's initial savings
We have found b = 5,000 b = 5{,}000 b = 5 , 000 , now we substitute it into equation ( 1 ) (1) ( 1 ) to find a a a :
Therefore, Rudi's initial savings was Rp 50,000.00 \text{Rp}50{,}000.00 Rp 50 , 000.00 .