We want to estimate the given product.

13.92 \times 2.7

To make our estimation, we will round each factor to the greatest place value. This makes it easier to use mental math. We need to follow a couple steps.

Look at the digit to the right of the place that is being rounded to.
- If the digit is less than $5,$ then the number in the rounded place remains the same.
- If the digit is $5$ or greater, add $1$ to the number in the rounded place.
After rounding, remove any decimal digits and convert into $0$ the non-decimal digits to the right of the place value being rounded.

In our case, we want to round

13.92

to the nearest ten and

2.7

to the nearest whole number. Therefore, for

13.92,

the place that we are rounding to is the tens place, so we will look at the number in the ones place. Similarly, for

2.7,

the place that we are rounding to is the ones place, so we will look at the number in the tenths place.

We can now multiply

10

and

3 .

Since

10 \times 3

is

30,

the product of

13.92

and

2.7

is about

30 .

Checking Our Answer

We can check our answer with a calculator. We will multiply $13.92$ by $2.7$ and compare the product with our approximation.

The product of $13.92$ and $2.7$ is $37.584 .$ This is close to our approximation, so we can say that our estimation is correct.

Exercise