Practice Data Types in CS Thinking

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

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Quick Recap

Categories that classify data values and determine which operations can validly be performed on them. Common data types include integers, floating-point numbers, strings, booleans, and arrays, each with its own set of permitted operations.

Different kinds of data (numbers, text, true/false) work differently.

Showing a random 20 of 50 problems.

Example 1

easy
What data type is the value 42?

Example 2

easy
Classify each: (a) 100, (b) 'OK', (c) 2.5, (d) true, (e) [1,2].

Example 3

medium
What is 10%310 \% 3 (the modulo/remainder operation)?

Example 4

challenge
A program reads ['3','1','2'] (strings) and sorts them; then reads [3,1,2] (ints) and sorts. Both sort fine here, but when would string vs int sorting differ? Give the order for ['10','9','2'].

Example 5

easy
What data type is the value 'hello'?

Example 6

hard
A shop tracks prices as integer cents to avoid floating-point error. A bag of apples costs $3.45\$3.45. Store it as what integer, and what is the total cents for 44 bags?

Example 7

challenge
Sorting strings ['9','10','100','2'] lexicographically vs numerically gives different orders. Show both sorted lists.

Example 8

medium
Adding integer 44 and float 1.51.5 gives what type and value?

Example 9

easy
What data type is the value 3.14?

Example 10

easy
Which operation joins 'cat' + 'fish' into 'catfish'?

Example 11

hard
A program stores prices as integers in pence (e.g., 499 for £4.99) rather than as floats. Explain two advantages of this approach.

Example 12

challenge
A function expects an integer count but receives the float 4.0. It uses count as a list size. Why might this error, and what is the safe fix?

Example 13

medium
Adding an integer 5 and a float 2.5 gives what type and value?

Example 14

medium
Why does comparing 0.1 + 0.2 == 0.3 sometimes return false in floating-point?

Example 15

easy
Which operation joins two strings: addition (concatenation) or subtraction?

Example 16

medium
A program reads user input as a string '25'. What happens if you try to calculate '25' + 10 without type conversion? What should you do instead?

Example 17

medium
Zero-based index 2 of 'PYTHON' returns which character?

Example 18

medium
What is the result of '3' + '4' when both are strings?

Example 19

hard
In integer division, what is −7//2-7 // 2 if the language rounds toward negative infinity?

Example 20

easy
Are '5' (a string) and 5 (an integer) the same data type? Yes or no.
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