LAMBDA for custom functions in Excel - Practice Problems & Coding Challenges

Challenge - 5 Problems

📊 Formula Result

intermediate

Output of a simple LAMBDA function

What is the output of this formula when entered in a cell?

=LAMBDA(x, x*3)(5)

Excel

=LAMBDA(x, x*3)(5)

A 8

B 5

C 15

D Error

💡 Hint

Think about what the LAMBDA function does with the input 5 and the formula x*3.

The LAMBDA function takes the input 5 as x and multiplies it by 3, resulting in 15.

❓ Function Choice

intermediate

Choose the correct LAMBDA to calculate area of a rectangle

Which LAMBDA formula correctly calculates the area of a rectangle given length and width?

A =LAMBDA(length, width, length+width)

B =LAMBDA(length, width, length/width)

C =LAMBDA(length, width, length-width)

D =LAMBDA(length, width, length*width)

💡 Hint

Area of a rectangle is length multiplied by width.

Option D multiplies length and width, which is the correct formula for area.

🎯 Scenario

advanced

Using LAMBDA with LET to calculate discounted price

You want to create a custom function using LAMBDA and LET to calculate a discounted price.

The discount is 10% of the original price.

Which formula correctly returns the discounted price when you input the original price?

A =LAMBDA(price, LET(discount, price*0.1, price-discount))(100)

B =LAMBDA(price, LET(discount, price+0.1, price-discount))(100)

C =LAMBDA(price, LET(discount, price-0.1, price-discount))(100)

D =LAMBDA(price, LET(discount, price*0.1, price+discount))(100)

💡 Hint

Discount is 10% of price, so multiply price by 0.1.

Option A correctly calculates discount as 10% of price and subtracts it from price.

📊 Formula Result

advanced

Output of recursive LAMBDA function for factorial

What is the output of this formula?

=LAMBDA(n, IF(n<=1, 1, n*FACT(n-1)))(4)

Assume FACT is the name of the LAMBDA function itself (recursive call).

Excel

=LAMBDA(n, IF(n<=1, 1, n*FACT(n-1)))(4)

A 24

B Error

C 10

D 120

💡 Hint

Think about how Excel handles recursive LAMBDA calls and if FACT is defined.

The formula references FACT inside itself but FACT is not defined, so it causes an error.

❓ data_analysis

expert

Analyzing output of a LAMBDA function with multiple parameters

Given the formula:

=LAMBDA(a, b, c, IF(a>b, c, a+b))(3, 5, 10)

What is the output?

Excel

=LAMBDA(a, b, c, IF(a>b, c, a+b))(3, 5, 10)

A 8

B 10

C 15

D Error

💡 Hint

Check the condition a>b and decide which value IF returns.

Since 3 is not greater than 5, the formula returns a+b = 3+5 = 8.

Practice

1. What does the LAMBDA function in Excel allow you to do?

easy

A. Convert text to numbers

B. Create your own custom formulas with parameters

C. Automatically sort data in a column

D. Create charts from data ranges

Solution

1. Step 1: Understand the purpose of LAMBDA

   LAMBDA lets you create custom formulas that can take inputs and return results, like your own mini-functions.

2. Step 2: Compare with other options

   Sorting, converting text, and creating charts are done by other Excel features, not LAMBDA.

3. Final Answer:

   Create your own custom formulas with parameters -> Option B

4. Quick Check:

   LAMBDA = custom formulas [OK]

Hint: LAMBDA = your own formula with inputs [OK]

Common Mistakes:

• Thinking LAMBDA sorts or formats data
• Confusing LAMBDA with built-in functions like SORT
• Assuming LAMBDA creates charts

2. Which of these is the correct syntax to define a LAMBDA function that adds two numbers x and y?

easy

A. =LAMBDA(x, y, x + y)

B. =LAMBDA(x + y)

C. =LAMBDA(x, y; x + y)

D. =LAMBDA(x, y, x - y)

Solution

1. Step 1: Check LAMBDA syntax

   LAMBDA syntax is =LAMBDA(parameter1, parameter2, ..., calculation). So =LAMBDA(x, y, x + y) is correct.

2. Step 2: Identify errors in other options

   =LAMBDA(x + y) misses parameters, C uses wrong separator (;), D subtracts instead of adding.

3. Final Answer:

   =LAMBDA(x, y, x + y) -> Option A

4. Quick Check:

   Correct LAMBDA syntax uses commas and parameters [OK]

Hint: LAMBDA needs parameters, commas, and a formula [OK]

Common Mistakes:

• Using semicolons instead of commas
• Omitting parameters
• Mixing up addition and subtraction

3. Given the formula =LAMBDA(x, y, x * y)(3, 4), what is the result shown in the cell?

medium

A. 7

B. 34

C. 12

D. Error

Solution

1. Step 1: Understand the LAMBDA call

   The LAMBDA takes two inputs x and y, then returns x * y. Here, x=3 and y=4.

2. Step 2: Calculate the multiplication

   3 multiplied by 4 equals 12.

3. Final Answer:

   12 -> Option C

4. Quick Check:

   3 * 4 = 12 [OK]

Hint: Multiply inputs inside LAMBDA to get result [OK]

Common Mistakes:

• Adding instead of multiplying
• Concatenating numbers as text
• Expecting an error from correct syntax

4. What is wrong with this LAMBDA formula? =LAMBDA(x, y, x + y(2, 3))

medium

A. Incorrect function call syntax inside LAMBDA

B. Missing closing parenthesis

C. Parameters x and y are not defined

D. LAMBDA cannot add numbers

Solution

1. Step 1: Analyze the formula structure

   The formula tries to add x + y(2, 3), but y is a parameter, not a function, so y(2, 3) is invalid.

2. Step 2: Identify the syntax error

   You cannot call parameters like functions inside LAMBDA. The correct call is outside the LAMBDA definition.

3. Final Answer:

   Incorrect function call syntax inside LAMBDA -> Option A

4. Quick Check:

   Parameters are values, not callable functions [OK]

Hint: Don't call parameters like functions inside LAMBDA [OK]

Common Mistakes:

• Trying to call parameters as functions
• Confusing LAMBDA parameters with named functions
• Ignoring parentheses placement

5. You want to create a reusable LAMBDA function named DOUBLE that doubles any number input. Which steps correctly create and use this function?

hard

A. Write =DOUBLE(5) without defining DOUBLE anywhere.

B. Write =LAMBDA(x, x*2)(5) directly in a cell without naming it.

C. Define DOUBLE as =LAMBDA(x, x+2) in Name Manager, then use =DOUBLE(5).

D. Define DOUBLE as =LAMBDA(x, x*2) in Name Manager, then use =DOUBLE(5) in a cell.

Solution

1. Step 1: Define the LAMBDA function correctly

   In Name Manager, create a name DOUBLE with formula =LAMBDA(x, x*2) to double input x.

2. Step 2: Use the named function in cells

   After defining, use =DOUBLE(5) in any cell to get 10.

3. Final Answer:

   Define DOUBLE as LAMBDA(x, x*2) and call DOUBLE(5) -> Option D

4. Quick Check:

   Named LAMBDA + call = reusable function [OK]

Hint: Name LAMBDA in Name Manager, then call by name [OK]

Common Mistakes:

• Using wrong formula (x+2 instead of x*2)
• Calling named function without defining it
• Trying to use LAMBDA without naming for reuse