Question

5 th term of an ap is 20 and the sum of its 7 th and 11 th term is 64 find common difference

Answer 1

Answer: common difference (d)=3

Step-by-step explanation:let

first term = a1=a

similarly

a2=a+d

a3=a+2d

a4=a+3d

.

.

an=a+(n-1)d

a5=a+(5-1)d=a+4d    ------eq 1

a7+a11=64

[a+(7-1)d]+[a+(11-1)d]=64

a+6d+a+10d=64

2a+16d=64   --------eq 2

from eq 2 & eq 1

2a+16d=64

a+4d=20   --------- *2

• 2a+16d=64

• 2a+8d=40

subtract

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           8d=24

           d=24/8=3