Grade 12 Coding Worksheet: Decimals Challenge Practice

Decimals Challenge Practice

Grade 12 Coding Decimals Challenge Practice Advanced 5 Questions 8 Views

Classroom Worksheet

Grade 12 Coding Worksheet: Decimals Challenge Practice

Decimals Challenge Practice

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Score______ / 5

Grade: Grade 12

Subject: Coding

Topic: Decimals

Time: 20 Minutes

Difficulty: Advanced

Questions: 5

Instructions:
Instructions: Answer all 5 questions. Show your reasoning or code logic where needed. Assume standard decimal arithmetic and common coding best practices. Write answers clearly and use appropriate precision when a question asks for rounding or formatting.

Skills Practiced:

Decimals
Coding
Critical Thinking
Problem Solving

1Question

A program stores the values 12.75, 0.6, and 3.125 as decimals. What is the exact sum, and what is the sum rounded to 2 decimal places?

2Question

In a financial app, a price of 49.99 is increased by 7.5% tax. What is the total cost before any rounding? Then write the total if the result must be displayed to 2 decimal places.

3Question

A developer uses floating-point numbers to compare two decimal values: 0.1 + 0.2 and 0.3. Explain why a direct equality check may fail, and state one coding strategy to compare them safely.

4Question

A data logger records temperatures every hour: 21.4, 21.6, 21.5, 21.7, and 21.8. Calculate the average temperature. Then determine what the average would be if each reading were stored with only 1 decimal place and the result rounded to 2 decimal places.

5Question

You are writing code for a checkout system. A customer buys 3 items at $12.49 each and 2 items at $7.95 each. The store gives a 10% discount on the subtotal, then adds 8.25% sales tax to the discounted amount. What final amount should be charged, rounded to 2 decimal places?

Answer Key

#	Answer
1	Exact sum: 16.475. Rounded to 2 decimal places: 16.48.
2	Total before rounding: 53.73925. Displayed to 2 decimal places: 53.74.
3	A direct equality check may fail because many decimal values cannot be represented exactly in binary floating-point, so 0.1 + 0.2 may produce 0.30000000000000004 instead of exactly 0.3. A safe strategy is to compare the difference using a small tolerance (for example, absolute difference < 0.000001) or use a decimal type designed for exact base-10 arithmetic.
4	Average temperature = (21.4 + 21.6 + 21.5 + 21.7 + 21.8) / 5 = 107.9 / 5 = 21.58. If each reading is already stored with 1 decimal place, the values remain the same here, so the average rounded to 2 decimal places is still 21.58.
5	Subtotal = 3(12.49) + 2(7.95) = 37.47 + 15.90 = 53.37. After 10% discount: 53.37 × 0.90 = 48.033. After 8.25% tax: 48.033 × 1.0825 = 51.9957225. Final amount rounded to 2 decimal places: $52.00.