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Arithmetic Progressions

Question
CBSEENMA10007523

In the following APs, find the missing terms in the boxes.

square comma space 38 comma space square comma space square comma space square comma space minus 22.





Solution

Let the first terms and the common difference of the given A .P. be a and d respectively.
Second term = 38
⇒ a + (2 – 1)d = 38
[∴ an = a + (n – 1) d]
⇒ a + d = 38 ...(i)
⇒ Sixth term = –22
⇒ a + (6 – 1 )d = –22
⇒ a + 5d = –22 ...(ii)
Solving (i) and (ii), we get
a = 53 d = –15
Therefore,
Third term = 53 + (3 –1 (–5)
[∵ an = a + (n – 1) d] = 53 – 30 = 23
Fourth term = 53 + (4 – 1) (–15)
[∵ an = a + (n – 1) d] = 8
Fifth term = 53 + (5 – 1) (–15)
[∵ = a + (n – 1) d] = –7
Hence, the missing terms in the boxes are :
box enclose 53 comma space box enclose 23 comma space box enclose 8 comma space box enclose negative 7 end enclose.