# Chairs

Determine the number of seats in the seventh row and ninth row, if 3rd row has 14 seats and in every next row of seats has five more than the previous row.

Result

a7 =  34
a9 =  44

#### Solution:

$a_{3}=14 \ \\ d=5 \ \\ a_{3}=a_{1}+2d \ \\ a_{1}=a_{3}-2 \cdot \ d=14-2 \cdot \ 5=4 \ \\ a_{7}=a_{1}+6 \cdot \ d=4+6 \cdot \ 5=34$
$a_{9}=a_{1}+8 \cdot \ d=4+8 \cdot \ 5=44$

Our examples were largely sent or created by pupils and students themselves. Therefore, we would be pleased if you could send us any errors you found, spelling mistakes, or rephasing the example. Thank you!

Leave us a comment of this math problem and its solution (i.e. if it is still somewhat unclear...):

Be the first to comment!

Tips to related online calculators
Do you have a linear equation or system of equations and looking for its solution? Or do you have quadratic equation?

## Next similar math problems:

1. AP - simple
Determine the first nine elements of sequence if a10 = -1 and d = 4
2. Third member
Determine the third member of the AP if a4=93, d=7.5.
3. Fifth member
Determine the fifth member of the arithmetic progression, if the sum of the second and fifth members equal to 73, and difference d = 7.
4. AS sequence
In an arithmetic sequence is given the difference d = -3 and a71 = 455. a) Determine the value of a62 b) Determine the sum of 71 members.
5. Determine AP
Determine the difference of the arithmetic progression if a3 = 7, and a4 + a5 = 71
6. Theorem prove
We want to prove the sentence: If the natural number n is divisible by six, then n is divisible by three. From what assumption we started?
7. Seats
Seats in the sport hall are organized so that each subsequent row has five more seats. First has 10 seats. How many seats are: a) in the eighth row b) in the eighteenth row
8. Sequence
Between numbers 1 and 53 insert n members of the arithmetic sequence that its sum is 702.
9. Digits
Show that if x, y, z are 3 consecutive nonzero digits, zyx-xyz = 198, where zyx and xyz are three-digit numbers created from x, y, z.
10. Difference AP 4
Calculate the difference of the AP if a1 = 0.5, a2 + a3 = -1.1
11. Sequence 2
Write the first 5 members of an arithmetic sequence a11=-14, d=-1
12. Holidays - on pool
Children's tickets to the swimming pool stands x € for an adult is € 2 more expensive. There was m children in the swimming pool and adults three times less. How many euros make treasurer for pool entry?
13. Sequence 3
Write the first 5 members of an arithmetic sequence: a4=-35, a11=-105.
14. Sequence
Write the first 6 members of these sequence: a1 = 5 a2 = 7 an+2 = an+1 +2 an
15. Cans
How many cans must be put in the bottom row if we want 182 cans arrange in 13 rows above so that each subsequent row has always been one tin less? How many cans will be in the top row?
16. Sequence
Write the first 7 members of an arithmetic sequence: a1=-3, d=6.
17. Arithmetic progression
In some AP applies: 5a2 + 7a5 = 90 s3 = 12 Find the first member a =? and difference d = ?