Solution:

Number of TVs produced in the seventh year = 1000

Number of TVs produced in the tenth year = 1450

t7 = 1000

t10 = 1450

a + 6 d = 1000 ----- (1)

a + 9 d = 1450 ----- (2)

(1) – (2)

Subtracting second equation from first equation

a + 6 d = 1000

a + 9 d = 1450

(-) (-) (-)

------------------

-3d = -450

d = -450/(-3)

d = 150

Substitute d = 150 in the first equation

a + 6(150) = 1000

a + 900 = 1000

a = 1000 -900

a = 100

Therefore number of TVs produced on the first year is 100

To find number of TVs produced in the 15th year year we have to find the 15th term of the A.P

tn = a + (n-1) d

t15 = 100 + (15-1) 150

t15 = 100 + 14(150)

= 100 + 2100

= 2200