Find the Opposite Number: Converting 2.1 to Its Negative Value

Question

Convert $2.1$ into its reciprocal form:

00:00 Find the reciprocal number

00:04 Break down the number into whole number and remainder

00:09 Convert from decimal to fraction

00:15 Convert from whole number to proper fraction

00:22 Add the fractions under a common denominator

00:37 Use the formula to find the reciprocal number

00:42 Any number multiplied by its reciprocal always equals 1

00:46 Switch between numerator and denominator to get the reciprocal number

00:51 And this is the solution to the question

To solve the problem, let's follow these steps:

Now, let's execute each step:

Step 1: Convert $2.1$ to a fraction. Since $2.1$ is a decimal, we express it as a fraction: $2.1 = \frac{21}{10}$ .

Step 2: Find the reciprocal. The reciprocal of $\frac{21}{10}$ is $\frac{10}{21}$ .

Step 3: Simplify. The fraction $\frac{10}{21}$ is already in its simplest form.

Thus, the reciprocal of $2.1$ is $\frac{10}{21}$ , which corresponds to choice 4.

Therefore, the opposite number of $2.1$ , interpreted as its reciprocal, is $\frac{10}{21}$ .

$\frac{10}{21}$