The sum of the 3rd and 7th terms of an A. P. is 38, and the 9th term is 37. Find the A. P?​

Let a be the first term in the arithmetic progression. Then each successive term differs from a by a fixed number c, so that

• first term = a

• second term = a + c

• third term = (a + c) + c = a + 2c

• fourth term = (a + 2c) + c = a + 3c

and so on. In general, the n-th term in the AP is a + (n - 1) c.

The sum of the 3rd and 7th terms is 38, so that

(a + 2c) + (a + 6c) = 38

==>   2a + 8c = 38

==>   a + 4c = 19 … … … [1]

The 9th term is 37, so

a + 8c = 37 … … … [2]

Subtracting [1] from [2] eliminates a and lets you solve for c :

(a + 8c) - (a + 4c) = 37 - 19

4c = 18

c = 18/4 = 9/2

Solve for a using either equations [1] or [2] :

a + 8 (9/2) = 37

a + 36 = 37

a = 1

Then the n-th term in the AP is 1 + 9/2 (n - 1) or 9/2 n - 7/2, where n ≥ 1.

answer: the price of one pound cabbage = $ 0.8

the point (10,8) represents that the cost of 10 pounds cabbage is $ 8

step-by-step explanation:

since, here is a proportional relation between the number of pounds of cabbage (x) and the price in dollars (y).

therefore, we can write,

⇒ y = k x

where k is the constant of proportionality.

now, point (5,4) is in the line.

thus, it will satisfies the above equation of line.

⇒ 4 = 5 k

⇒ k = 0.8

thus, the equation of the line is,

y = 0.8 x

a) for x = 1,

y = 0.8

therefore, the cost of one pound of cabbage is 0.8 dollars.

b) in the below graph (10,8) represents that the cost of 10 pounds of cabbage is 8 dollars.