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

This topic has expert replies
Moderator
Posts: 2058
Joined: Sun Oct 29, 2017 4:24 am
Thanked: 1 times
Followed by:5 members

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

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 each year.

Answer: B

Source: GMAT Prep

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

M7MBA wrote:
Thu Oct 07, 2021 2:31 am
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 each year.

Answer: B

Source: GMAT Prep
Given: A poplar tree was 3 feet high when it was planted on January 1, 1970.

Target question: During what year did it pass the height of 20 feet?

Statement 1: On January 1, 1973, it was 24 feet high.
Important: This means the tree grew 24 feet in 3 years. HOWEVER, we cannot then conclude that the tree grew 8 feet each year, since we're given no information to suggest the tree grew at a constant rate.
This means the tree's height could have passed 20 feet in 1970, 1971, or 1972
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: It doubled its height during each year.
Perfect! We now know the following:
January 1, 1970: height = 3 feet
January 1, 1971: height = 6 feet
January 1, 1972: height = 12 feet
January 1, 1973: height = 24 feet
So, the tree's height passed 20 feet in 1972
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image