SAT Math Practice Question #279 (Hard (740)) | Test Citadel
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SAT Math Difficulty: Hard (740)

Digital SAT Math Practice Question #279

Test your problem-solving accuracy on this official-caliber item. Select an answer choice to check your reasoning instantly.

A radioactive isotope decays such that its mass decreases by \( 18\% \) every 4 hours. If the initial mass of the isotope is \( M_0 \) grams, which of the following expressions represents the mass of the isotope, in grams, after \( d \) days?
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Socratic AI Engine Step-by-Step Derivation
0ms Precomputed
Tactical Insight (Hint 1)

Express the growth/decay rate in factor form: \( A = P(1 \pm r)^t \). Beware whether \( t \) is in years, months, or quarters.

Elimination Framework (Hint 2)

Elimination Shortcut: Check the extremes or test answer choices starting with C to binary search the correct magnitude.

Masterclass Solution & Distractor Trap Analysis

This question tests two major concepts simultaneously: calculating percentage decrease and performing unit conversions within exponents. Step 1: Set up the base of the exponential function. The mass *decreases* by \( 18\% \) every cycle. Th...

Distractor Analysis: Trap choice eliminates careless test-takers who confuse roots with coordinates...

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