Advertisements
Advertisements
Question
The 5th term of an AP is 20 and the sum of its 7th and 11th terms is 64. The common difference of the AP is ______.
Options
4
5
3
2
MCQ
Fill in the Blanks
Advertisements
Solution
The 5th term of an AP is 20 and the sum of its 7th and 11th terms is 64. The common difference of the AP is 3.
Explanation:
Let a be the first term and d the common difference.
t5 = a + 4d
= 20
t7 + t11 = (a + 6d) + (a + 10d)
= 2a + 16d
= 64
Substitute a = 20 – 4d into 2a + 16d = 64:
2(20 − 4d) + 16d = 64
⇒ 40 + 8d = 64
⇒ d = 3
shaalaa.com
Is there an error in this question or solution?
