Question

The power $(?)$ of $10$ that makes the following equation true is .
$3\times 7\times {10}^{?}=210$

• A. $0$
• B. $1$
• C. $2$
• D. $3$
• E. $4$

Answer 1

The correct option is B $1$

$\underset{–}{\text{Need to find:}}$ The exponent $(?)$ in $3\times 7\times {10}^{?}=210$

We can simplify the given equation as
$3\times 7\times {10}^{?}=210$
$\Rightarrow (3\times 7)\times {10}^{?}=210$
$\Rightarrow 21\times {10}^{?}=210$
$\Rightarrow 21.0\times {10}^{?}=210$

We know that multiplying $21.0$ by $10$ moves the decimal point $1$ unit to the right, i.e.,
$21.0\times 10=210.0=210$

$\therefore \underset{–}{3\times 7\times {10}^1=21\times {10}^1=210}$

Hence, the exponent $(?)$ in $3\times 7\times {10}^{?}=210$ is $\underset{–}{1}$.