## Explanation

This formula uses the named range **key** (C4:G4) for convenience only. Without the named range, you'll want to use an absolute reference so the formula can be copied.

In cell I7, we have this formula:

```
=SUM(--(C7:G7=key))
```

working from the inside-out, this expression is evaluated first:

```
C7:G7=key // compare answers to key
```

The result is an array of TRUE FALSE values like this:

```
{TRUE,TRUE,TRUE,FALSE,TRUE}
```

TRUE values indicate a correct answer, FALSE values indicate an incorrect answer.

To coerce the TRUE and FALSE values to numbers, we use a double negative:

```
--({TRUE,TRUE,TRUE,FALSE,TRUE}) // get 1's and 0's
```

The is an array of 1's and 0's delivered directly to the SUM function:

```
=SUM({1,1,1,0,1}) // sum correct
```

The SUM function then returns the final result, 4.

### Incorrect answers

The formula in J7 counts incorrect answers in almost the same way:

```
=SUM(--(C7:G7<>key))
```

The only difference is that we are now using the not equal to (<>) logical operator:

```
=SUM(--(C7:G7<>key))
=SUM(--({FALSE,FALSE,FALSE,TRUE,FALSE}))
=SUM({0,0,0,1,0})
=1
```

### Percent correct

The formula in K7 calculates the percentage of correct answers like this:

```
=I7/COUNTA(key) // divide correct by total
```

Cell I7 already contains the count of correct answers. This is divided by the total count of quiz answers, which is calculated with the COUNTA function:

```
COUNTA(key) // count total
```

The result is formatted with the percentage number format.