M7MBA wrote: ↑Thu Oct 29, 2020 1:09 pm
A poplar tree was 3 feet high when it was planted on January 1, 1970. During what year did it pass the height of 20 feet?
(1) On January 1, 1973, it was 24 feet high.
(2) It doubled its height during each year.
Answer:
B
Source: GMAT Prep
We need to find the year when the height was \(20\) feet.
Given: height \(= 3\)ft on \(1\)st Jan \(1970\)
Statement 1: On January \(1, 1973\), it was \(24\) feet high.
We do not know the rate of growth it can be
\(1\)st Jan \(1970.\, 3\, 3.\, 3\)
\(1\)st Jan \(1971.\, 10\, 12.\, 10\)
\(1\)st Jan \(1972.\, 16\, 22.\, 20\)
\(1\)st Jan \(1973.\, 24\, 24.\, 24\)
No unique answer. Not Sufficient \(\Large{\color{red}\chi}\)
Statement 2: It doubled its height during each year.
i.e.
\(1\)st Jan \(1970.\, 3\)
\(1\)st Jan \(1971.\, 6\)
\(1\)st Jan \(1972.\, 12\)
\(1\)st Jan \(1973.\, 24\)
it means height crossed \(20\) ft during \(1972\). Sufficient \(\Large{\color{green}\checkmark}\)
Therefore,
B
