By the end of the school year. Terry had passed 80% of his science tests. If Terry failed 4 science tests, how many science tests did Terry pass?

Options

A. `12`
B. `15`
C. `16`
D. `18`

Answer

To solve the problem step by step, we can follow these steps:

### Step 1: Understand the problem
Terry passed 80% of his science tests and failed 4 tests. We need to find out how many tests he passed.

### Step 2: Define the total number of tests
Let the total number of science tests Terry took be denoted as \( x \).

### Step 3: Determine the percentage of tests failed
Since Terry passed 80% of his tests, he must have failed 20% of his tests. This can be expressed mathematically as:
\[ \text{Failed tests} = 20\% \text{ of } x = 0.2x \]

### Step 4: Set up the equation
We know from the problem that Terry failed 4 tests. Therefore, we can set up the equation:
\[ 0.2x = 4 \]

### Step 5: Solve for \( x \)
To find the total number of tests \( x \), we can rearrange the equation:
\[ x = \frac{4}{0.2} \]
Calculating this gives:
\[ x = 20 \]

### Step 6: Calculate the number of tests passed
Now that we know Terry took a total of 20 tests, we can find out how many he passed. Since he passed 80% of his tests, we calculate:
\[ \text{Passed tests} = 80\% \text{ of } 20 = 0.8 \times 20 = 16 \]

### Final Answer
Terry passed **16 science tests**.

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