Arithmetic expressions ($add, $multiply, $divide) in MongoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add two fields 'price' and 'tax' in a MongoDB aggregation pipeline.

MongoDB

{ $project: { totalCost: { $add: ["$price", [1] ] } } }

Drag options to blanks, or click blank then click option'

A"$tax"

B"tax"

C"$total"

D"cost"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the $ before the field name

Using the field name as a string without $

In MongoDB aggregation, to refer to a field, you use "$" before the field name. So "$tax" correctly refers to the 'tax' field.

2fill in blank

medium

Complete the code to multiply 'quantity' by 'price' to get 'total' in a MongoDB aggregation pipeline.

MongoDB

{ $project: { total: { $multiply: ["$quantity", [1] ] } } }

Drag options to blanks, or click blank then click option'

A"price"

B"$price"

C"cost"

D"amount"

Attempts:

3 left

💡 Hint

Common Mistakes

Using field names without $

Using incorrect field names

Use "$price" to correctly reference the 'price' field in the aggregation pipeline.

3fill in blank

hard

Fix the error in the code to divide 'total' by 'count' in a MongoDB aggregation pipeline.

MongoDB

{ $project: { average: { $divide: ["[1]", "$count" ] } } }

Drag options to blanks, or click blank then click option'

A"$total"

B"total"

C$total

Dtotal

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted field names

Omitting the $ prefix

To refer to a field inside an aggregation expression, you must use "$" before the field name and wrap it in quotes.

4fill in blank

hard

Fill both blanks to calculate the total price including tax by adding 'price' and the product of 'price' and 'taxRate'.

MongoDB

{ $project: { totalPrice: { $add: ["$price", { $multiply: ["$price", [1] ] } ] } } }

Drag options to blanks, or click blank then click option'

A"$tax"

B"taxRate"

C"$taxRate"

D"tax"

Attempts:

3 left

💡 Hint

Common Mistakes

Not using $ before 'taxRate'

Using incorrect field names

To multiply 'price' by 'taxRate', both fields must be referenced with a $ prefix inside strings.

5fill in blank

hard

Fill all three blanks to calculate the average price per item after discount: subtract 'discount' from 'price', then divide by 'quantity'.

MongoDB

{ $project: { avgPrice: { $divide: [ { $subtract: ["[1]", "[2]" ] }, "[3]" ] } } }

Drag options to blanks, or click blank then click option'

A"$price"

B"$discount"

C"$quantity"

D"price"

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting $ before field names

Using field names without quotes

Each field must be referenced with a $ prefix inside quotes to be correctly used in aggregation expressions.