NCERT Class X Chapter 5: Arithmetic Progression Example 16(ii)

NCERT Class X Chapter 5: Arithmetic Progression Example 16(ii)

Question:

A manufacturer of TV sets produced 600 sets in the third year and 700 sets in the seventh year. Assuming that the production increases uniformly by a fixed number every year, find : the production in the 10th year

Given:

Production in the 3rd year = 600 sets
Production in the 7th year = 700 sets

To Find:

Production in the 10th year

Formula:

Let the production in the nth year be given by the arithmetic progression: an = a1 + (n-1)d, where a1 is the production in the first year and d is the common difference.

Solution:

Let a3 = 600 and a7 = 700. Then we have:

a3 = a1 + 2d = 600 ⇒ a1 = 600 - 2d

a7 = a1 + 6d = 700

Substituting a1 = 600 - 2d:

(600 - 2d) + 6d = 700

4d = 100

d = 25

Now, we find a1:

a1 = 600 - 2(25) = 600 - 50 = 550

Finally, we find a10:

a10 = a1 + 9d = 550 + 9(25) = 550 + 225 = 775

Result:

The production in the 10th year is 775 sets.

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