Question

the hcf of a number is 7 the lcm 42 and the second number is 21 what is the first number ?

Answer 1

• As per the data given in the question, we have to determine the required number.

       Given data:-$HCF=7$ and $LCM=42.$

       Second number= $21.$

       To find:- the first number=?

       Solution:-

       Let the required number be $x$.

       As,we know that,

       The Product of two numbers is $hcf\times lcm.$

        Therefore,

       $\Rightarrow 21\times second\ number=7\times42\\\Rightarrow x=\frac{7\times42}{21}\\\Rightarrow x=7\times2=14.$

      Hence, the first number is $14.$

Answer 2

Given data,

HCF of a numbers is $7$

LCM of a number is $42$

The second number is given as $21$

We have to find out the first number.

To calculate the second number we use a formula.

Formula:

Product of two numbers = LCM $\times$ HCF

Let the first number be $x$

$x\times 21=7\times42$

$x=\frac{7\times42}{21}$

$x=7\times2$

$x=14$

The value of $x$ is $14$

Therefore, the first number is $14$