If in an AP, ratio of 4th and 9th term is 1:3, find the ratio of 12th term and 5th term.
yasummu:
is it 5th or 15th?
Answers
Answered by
120
a4/a9 = 1/3
a+3d/a+8d = 1/3
(a+3d)3 = (a+8d)
3a+9d = a+8d
2a+d = 0
d = -2a
a12/a5
a+11d/a+4d
=a+11*(-2a)/a+4*(-2a)
=a-22a/a-8a
= -21a/-7a
=21/7
=3/1
=3:1
a+3d/a+8d = 1/3
(a+3d)3 = (a+8d)
3a+9d = a+8d
2a+d = 0
d = -2a
a12/a5
a+11d/a+4d
=a+11*(-2a)/a+4*(-2a)
=a-22a/a-8a
= -21a/-7a
=21/7
=3/1
=3:1
Answered by
46
Given that ratio is 1:3.
That means, a9 = 3*a4.
Need to find, a12/a5.
a9=a+8d
a4=a+3d
a+8d=3a+9d
d=-2a
a12=a+11d=-21a
a5=a+4d=-7a
So ratio of a12 to a5 = -21a:-7a or 3:1//
That means, a9 = 3*a4.
Need to find, a12/a5.
a9=a+8d
a4=a+3d
a+8d=3a+9d
d=-2a
a12=a+11d=-21a
a5=a+4d=-7a
So ratio of a12 to a5 = -21a:-7a or 3:1//
Similar questions