Difficulty: Easy
Correct Answer: 78
Explanation:
Introduction / Context:
This problem checks your understanding of the order of operations, often remembered by the rule BODMAS or PEMDAS. You must correctly handle brackets or parentheses, multiplication, and subtraction in the expression 8(6 + 5) − 10. Many errors come from doing operations in the wrong order or making small arithmetic mistakes.
Given Data / Assumptions:
Concept / Approach:
The order of operations tells us to compute parentheses first, then multiplication or division, and finally addition or subtraction. So we must first add 6 and 5, then multiply by 8, and finally subtract 10. This systematic approach prevents mistakes that come from working left to right without regard to operation priority.
Step-by-Step Solution:
Step 1: Evaluate the expression inside the parentheses: 6 + 5.
Step 2: Compute 6 + 5 = 11.
Step 3: Now the expression becomes 8 * 11 − 10.
Step 4: Perform the multiplication: 8 * 11 = 88.
Step 5: Now subtract 10 from 88: 88 − 10 = 78.
Step 6: Therefore, the value of the expression is 78.
Verification / Alternative check:
You can quickly verify your answer by doing the calculation again in a slightly different layout. For example, note that 8 * (6 + 5) is 8 * 11, and 8 * 10 is 80, while 8 * 1 is 8, so 80 + 8 = 88. Subtracting 10 then gives 78. Using mental arithmetic in two ways that agree gives confidence in the result.
Why Other Options Are Wrong:
Common Pitfalls:
A very common mistake is to start multiplying 8 by 6 before dealing with the entire bracket, which violates the order of operations. Another pitfall is careless subtraction at the final step. Writing each step clearly and respecting parentheses prevents these simple but costly errors in timed tests.
Final Answer:
The correct value of the expression 8(6 + 5) − 10 is 78.
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