Question

How many numbers are there between two numbers $3500$ and $4000$ which are divisible by $24,21$, and $28$?

• A. $5$
• B. $3$
• C. $4$
• D. $6$

Answer 1

Answer: (B)

$3$

Factors of
$24=2\times 2\times 2\times 3,21=3\times 7,28=2\times 2\times 7$
LCM of $21,24,28=168$
$168\times 20=3360$
$168\times 21=3528$
$168\times 22=3696$
$168\times 23=3864$
$168\times 24=4032$
There are only $3$ numbers between $3500$ and $4000$.
Therefore, $B$ is the correct answer.