Question

Elijah is very consistent on her running practice. She used to run $150$ miles on a monthly basis. How many miles Elijah will run in $10$ years?

• A. $1,800$
• B. $10,800$
• C. $1,500$
• D. $18,000$

Answer 1

The correct option is D $18,000$

We know, $1$ year contains $12$ months.
$\therefore$ $10$ years contain $12\times 10=120\text{months}$

In $1$ month, Elijah runs $150$ miles.
$\therefore$ In $120$ months, Elijah will run $(150\times 120)$ miles

Next, we are going to discuss the multiplication of three digits
numbers with carry, i.e., $150\times 120$.

To solve $150\times 120$, we follow the below steps:

$\bullet$ First we write the bigger number at the top and smaller number just below of it with a proper alignment of one's place.


$\bullet$ After multiply $150$ with $0$, we get $000$.


$\bullet$ For the next multiplication step, we leave one's place (denoted by faded $0$), and start from ten's place.

We first multiply $2$ with $0$, which is $0$. The next number, we get $2\times 5=\underset{–}{1}0$, where $1$ is carrying over to the next multiplication, $2\times 1$.

Hence, we get the next number as $(2\times 1)+1=2+1=3$.


$\bullet$ For the next multiplication step, we leave one's and ten's places (denoted by faded $0$), and start from hundred's
place.

After multiply $150$ with $1$, we get $150$.


$\bullet$ Next, we add $000$, $3000$ and
$15000$ to get the final result.



$\therefore \underset{–}{150\times 120=18,000}$

Hence, Elijah will run $18,000$ miles in $10$ years, i,e., option (d.) is the correct one.