Q2 of 67 Page 74

If 18, a, b, -3 are in the arithmetic progression then a + b =

Since they are in arithmetic progression their common difference is same.
⇒ a – 18 = b – a = -3 – b
⇒ a – 18 = -3 – b
⇒ a + b = 18 – 3
⇒ a + b = 15.

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10

A manufacture of TV sets produces 600 TV sets in the third year and 700 TV sets in seventh year. Assuming that the production increases, uniformly by a fixed number every year, find
(i) the production in the 1st year
(ii) the production in the 10th year
(iii) the total production in first 7 years.

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