Question 63

If 7 times the seventh term of an Arithmetic Progression (AP) is equal to 11 times its eleventh term, then the 18th term of the AP will be

Solution

Let the first term of the AP be $$a$$ and the common difference = $$d$$

7th term = $$A_7=a+6d$$

11th term = $$A_{11}=a+10d$$

According to ques,

=> $$7 \times (a+6d)=11 \times (a+10d)$$

=> $$7a+42d=11a+110d$$

=> $$11a-7a=42d-110d$$

=> $$4a=-68d$$

=> $$a=-17d$$

=> $$a+17d = 0 = A_{18}$$

=> Ans - (B)

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