Find the no. of multiples of 6 lying between 75 and 750.

 the list of such no.s are,

78,84.90....744

a = 78

d = 84 - 78 = 6

An = 744

An = a + (n-1)d

744 = 78 + (n-1)6

744 - 78 + (n-1)6

666 = (n-1)6

111 = (n-1)

111 + 1 = n

112 = n

There are 112 terms or no.s multiples of 6 lying between 75 and 750.