If product of first 10 natural numbers is equals to  $2^a\times 3^b\times 5^c\times 7^d$, then  $a+b+c+d=$

$1\times 2\times 3\times 4\times 5\times 6\times 7\times 8\times 9\times 10=2^a\times 3^b\times 5^c\times 7^d$

$2^1\times 3^1\times 2^2\times 5^1\times 2^1\times 3^1\times 7^1\times 2^3\times 3^2\times 2^1\times 5^1=2^a\times 3^b\times 5^c\times 7^d$

$2^8\times 3^4\times 5^2\times 7^1=2^a\times 3^b\times 5^c\times 7^d$

$a=8,b=4,c=2,d=1$

$a+b+c+d=8+4+2+1=15$