Question

The ratio of 5th and 3rd term of an ap is 2:5 find the ratio of its 15th and 7th term

Answer 1

$a5 \div a3 = \frac{2}{5} \\ \frac{a + 4d}{a + 2d} = \frac{2}{5 }$
5a+20d=2a+4d
3a=-16d
a=-16/3
a15/a7=(a+14d)/(a+6d)
=(-16/3d+14d)/(-16/3d+6d)
=((-16+42)d/3)/((_16+18)d/3)
=(26d/3)/(2d/3)
=26/2
=13/1