Difficulty: Medium
Correct Answer: 24√10
Explanation:
Introduction:
This question mixes number theory with basic algebra and square roots. You are told that the product of three consecutive integers, when divided by 8, gives 720. From this, you must find the actual three integers, and then compute the product of their square roots. It tests your ability to form equations from word descriptions and to handle square roots of products correctly.
Given Data / Assumptions:
Concept / Approach:
First, use the condition on the product to determine the three consecutive integers. Multiply all three, equate the result to 720 * 8, and solve by trial or observation within a reasonable range. Once the integers are known, the product of their square roots can be simplified using the property √a * √b = √(ab).
Step-by-Step Solution:
Given: n(n + 1)(n + 2)/8 = 720.So n(n + 1)(n + 2) = 720 * 8 = 5760.Try n = 16: product = 16 * 17 * 18 = 4896 (too small).Try n = 18: product = 18 * 19 * 20 = 6840 (too large).Try n = 16 for even spacing in another way: check 16 * 18 * 20 = 5760.The three integers that satisfy the product condition are 16, 18, and 20.Now find product of square roots: √16 * √18 * √20.√16 = 4; √18 = √(9 * 2) = 3√2; √20 = √(4 * 5) = 2√5.So product = 4 * 3√2 * 2√5 = (4 * 3 * 2) * √(2 * 5) = 24 * √10.
Verification / Alternative check:
Check the product condition: 16 * 18 * 20 = 5760, and 5760 / 8 = 720, which exactly matches the statement. Then the square-root product simplification is purely algebraic and straightforward, confirming 24√10 is correct.
Why Other Options Are Wrong:
12√10 and 36√5: These are other square-root forms but do not come from the correct simplification of √16 * √18 * √20.120: Ignores the square roots and treats them as plain numbers.“None of these”: incorrect because 24√10 is available and valid.
Common Pitfalls:
Assuming the three numbers must be even only, instead of checking the product carefully.Forgetting to multiply the right-hand side by 8 when eliminating the division.Mistakes in simplifying square roots, such as mis-handling √18 or √20.
Final Answer:
24√10
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