To find out how many grapes Reza ate yesterday using equivalent ratios, we can start by understanding the relationship between the number of grapes he ate today and yesterday.
We know that he ate 20 grapes today, and this is stated to be 400% of what he ate yesterday. The percentage can be converted to a fraction for easier calculation: 400% means 400 out of 100, which simplifies to 4 when we convert it to a ratio.
Let \( x \) represent the number of grapes Reza ate yesterday. According to the problem, we can express the relationship as follows:
\[ 20 = 4x \]
This equation states that 20 grapes (the amount he ate today) equals 4 times the number of grapes he ate yesterday.
Next, we solve for \( x \):
- Divide both sides of the equation by 4:
\[ x = \frac{20}{4} \]
- Simplify the division:
\[ x = 5 \]
So, Reza ate 5 grapes yesterday.
To verify, we can check the relationship:
- If he ate 5 grapes yesterday, then 400% of that amount is \( 4 \times 5 = 20 \), which matches the number of grapes he ate today.
Thus, the number of grapes Reza ate yesterday is indeed 5.