The list of two digit numbers which are multiples of 5 are
15, 20, 25, 30,...........95
We have, a = 15, d = 5, an = 95
We know, an = a + (n – 1) d
⇒ 95 = 15 + (n – 1)5
⇒ 95 = 15 + 5n – 5
⇒ 95 = 10 + 5n
⇒ 5n = 85
⇒ n = 17
Hence, there are 17 two digit numbers lie between 10 and 100 which are multiples of 5.