Question a-scie
A scientist studying the life cycle of dragonflies counted the number of dragonflies in a certain habitat each day for days. On February , there were dragonflies in the habitat. The percent increase in the number of dragonflies in the habitat from January to February was . How many dragonflies were in the habitat on January ?
A scientist studying the life cycle of dragonflies counted the number of dragonflies in a certain
Hard-difficulty · SAT Math · Percentages — Finding original amount from percent change. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.
Answer explanation
Choice A is correct. It’s given that a scientist studying the life cycle of dragonflies counted the number of dragonflies in a certain habitat each day for days. It’s also given that on February , there were dragonflies in the habitat and that the percent increase in the number of dragonflies in the habitat from January to February was . This can be represented by the equation
, where represents the number of dragonflies in the habitat on January . This equation can be rewritten as . Dividing both sides of this equation by yields . Therefore, there were dragonflies in the habitat on January .
Choice B is incorrect and may result from conceptual or calculation errors.
Choice C is incorrect and may result from conceptual or calculation errors.
Choice D is incorrect and may result from conceptual or calculation errors.
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