Question

{ 5/21+2/15 } + 2/21

Answer 1

от перемены мест слагаемых сумма не меняется

1)5/21+2/21=7/21=1/3

2)1/3+2/15=5/15+2/15=7/15

Answer 2

To add these fractions together, you need to find a common denominator for all of them. In this case, the least common denominator (LCD) is 105. Here's how you can add them step by step:

1. Convert each fraction to have a denominator of 105:

   • $\frac{5}{21}$ becomes $\frac{5 \cdot 5}{21 \cdot 5} = \frac{25}{105}$
   • $\frac{2}{15}$ becomes $\frac{2 \cdot 7}{15 \cdot 7} = \frac{14}{105}$
   • $\frac{2}{21}$ becomes $\frac{2 \cdot 5}{21 \cdot 5} = \frac{10}{105}$

2. Now that all fractions have a common denominator of 105, you can add them:

   $\frac{25}{105} + \frac{14}{105} + \frac{10}{105}$

3. Add the numerators together while keeping the denominator the same:

   $\frac{25 + 14 + 10}{105}$

4. Simplify the numerator:

   $\frac{49}{105}$

5. Reduce the fraction to its simplest form by dividing both the numerator and denominator by their greatest common divisor, which is 7:

   $\frac{7}{15}$

So, $\frac{5}{21} + \frac{2}{15} + \frac{2}{21} = \frac{7}{15}$.