How many numbers are there in between 55 and 3815, which are multiples of 5 and divisible by 3?

Correct Answer: 251
For a number to be a multiple of 5 and divisible by 3, it should be divisible by 15. Between 55 and 3815, the first and last number divisible by 15 are 60 and 3810 respectively. i.e., a=5, d=15, Tn=3810 Tn = a + (n-1)d 3810 = 60 + (n-1)*15 Therefore, n=251