Question

There are four prime numbers written in ascending order. The product of the first three is $385$ and that of the last three is $1001$. The last number is

• A. $11$
• B. $13$
• C. $17$
• D. $19$

Answer 1

The correct option is B $13$

Let the prime numbers be

$a<b<c<d$

So, $abc=358$ and $bcd=1001$

Divide $bcd$ by $abc$, we get

$\frac{bcd}{abc}=\frac{1001}{385}$

$\Rightarrow \frac{d}{a}=\frac{13}{5}$
Since, $d$ and $a$ are prime numbers, so the last prime number, $d=13$ and the first prime number, $a=5$.

Hence, option B.