Floating point types (float, double, decimal) in C Sharp (C#) - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of floating point addition with float and double

What is the output of this C# code snippet?

C Sharp (C#)

float a = 0.1f;
double b = 0.1;
Console.WriteLine(a == b);

A True

B Runtime exception

C False

D Compilation error

💡 Hint

Consider how float and double represent decimal numbers differently.

The float and double types have different precision and internal representation. Comparing a float to a double directly with == returns false because 0.1f and 0.1 (double) are not exactly the same value.

❓ Predict Output

intermediate

Decimal precision in financial calculation

What is the output of this C# code?

C Sharp (C#)

decimal price = 19.99m;
decimal quantity = 3m;
decimal total = price * quantity;
Console.WriteLine(total);

A 59.969999999999999

B 59.97

C 60

D Compilation error

💡 Hint

Decimal type is designed for exact decimal representation.

Decimal type stores exact decimal values, so multiplying 19.99 by 3 results in exactly 59.97 without floating point rounding errors.

❓ Predict Output

advanced

Result of mixed type arithmetic with float, double, and decimal

What is the output of this C# code?

C Sharp (C#)

float f = 1.5f;
double d = 2.5;
decimal m = 3.5m;
var result = f + (float)d;
Console.WriteLine(result);

A 4

B 3.9999998

C 4.0

D Compilation error

💡 Hint

Consider whether these values are exactly representable in float precision.

Both 1.5 and 2.5 are exactly representable in single-precision float (and double). Casting double 2.5 to float gives the exact value 2.5f, and 1.5f + 2.5f = 4.0f exactly, which Console.WriteLine prints as "4".

❓ Predict Output

advanced

Effect of floating point precision on equality check

What does this C# code print?

C Sharp (C#)

double x = 0.1 + 0.2;
bool equal = x == 0.3;
Console.WriteLine(equal);

A Runtime exception

B True

C Compilation error

D False

💡 Hint

Floating point addition can introduce small errors.

Due to floating point precision, 0.1 + 0.2 is not exactly 0.3 in double precision, so the equality check returns false.

🧠 Conceptual

expert

Choosing the correct floating point type for currency calculations

Which floating point type should you use in C# for precise currency calculations to avoid rounding errors?

A decimal

B double

C float

D int

💡 Hint

Think about which type stores decimal numbers exactly without binary rounding errors.

The decimal type is designed for financial and monetary calculations because it stores decimal numbers exactly, avoiding rounding errors common in float and double.