Question

In an A.P 7th term is 23 and 29th term is 85. Find the 18th term in the A.P
?​

Answer 1

Answer:

In AP

Given :

• a7 = 23
• a9 = 85

Solution :

• a + 6d = 23 ~ equation 1
• a + 8d = 85 ~ equation 2

Solving equation 1 and 2

• (-2d) = (-62)
• 2d = 62
• d = 62/2
• d = 31
• a + 6d = 23
• a + 6(31) = 23
• a + 186 = 23
• a = 23 - 186
• a = (-163)

a18 = a + 17d

• a18 = (-163) + 17(31)
• a18 = (-163) + 527
• a18 = 364

Answer 2

Answer:

Difference Between 18 and 7= Distance between 18and 29

so the 18th term will be mean of 7th and 29th term

18th term=(23+85)/2=54