Question

solve this explanation

Answer 1

TO FIND :-

Number of numbers which are multiples of both 3 and 5 in first 100 natural numbers

SOLUTION :-

As we know that natural numbers starts from 1

N = {1,2,3,4......}

Multiples of 3 in first 100 natural numbers = {3,6,9,12,15......99}

Multiples of 5 in first 100 natural numbers = {5,10,15......100}

Multiples of both 3 and 5 in first 100 natural numbers = {15,30....90}

Here

a = 15

d = 15

an = 90

an = a + (n-1)d

90 = 15 + (n-1)15

75 = (n-1)15

n - 1 = 75/15

n - 1 = 5

n = 5 + 1

n = 6

Therefore the answer is option D