Number of Stairs Between Floors

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pierce22884: Junior | Next Rank: 30 Posts; Posts: 13; Joined: Sun Sep 07, 2008 4:34 pm; Location: Dallas, TX

by pierce22884 » Fri Feb 19, 2010 2:50 pm

If the two floors in a certain building are 9 feet apart, how many steps are there in a set of stairs that extends from the first floor to the second floor of the building?

1) Each step is (3/4) foot high.

2) Each step is is 1 foot wide.

OA: A

Please help me understand as to why.

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Source: Beat The GMAT — Data Sufficiency | Fri Feb 19, 2010 2:50 pm

Amiman: Junior | Next Rank: 30 Posts; Posts: 24; Joined: Wed Jan 20, 2010 3:50 pm

by Amiman » Fri Feb 19, 2010 3:03 pm

1 is suff
2 talks about wide and not height so not suff

Ans A

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pierce22884: Junior | Next Rank: 30 Posts; Posts: 13; Joined: Sun Sep 07, 2008 4:34 pm; Location: Dallas, TX

by pierce22884 » Fri Feb 19, 2010 3:11 pm

You need to know the width also. The stairs are not going to be stacked (3/4) foot high on top of each other the WIDTH must be know.........

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Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members; Location: Toronto; Thanked: 1710 times; GMAT Score:800

by Stuart@KaplanGMAT » Fri Feb 19, 2010 4:00 pm

pierce22884 wrote:You need to know the width also. The stairs are not going to be stacked (3/4) foot high on top of each other the WIDTH must be know.........

No you don't.

Whether the steps are 5 feet wide each or 1 inch wide, if we know the height of each step we know how many steps it takes to gain 9 feet of altitude.

As a complete aside, I think you have depth confused with width (although the depth of the steps is also irrelevant to answering the question posed).

Height of step = vertical distance;
width of step = side to side distance; and
depth of step = how far from the edge of one step does the next step begin.

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shashank.ism: Legendary Member; Posts: 1022; Joined: Mon Jul 20, 2009 11:49 pmFollowed by: 2 members; Location: Gandhinagar; Thanked: 41 times

by shashank.ism » Sun Feb 21, 2010 4:50 am

pierce22884 wrote:If the two floors in a certain building are 9 feet apart, how many steps are there in a set of stairs that extends from the first floor to the second floor of the building?

1) Each step is (3/4) foot high.

2) Each step is is 1 foot wide.

[spoiler]OA: A[/spoiler]

Please help me understand as to why.

two floors are 9 feet apart..
St.1 Each step is (3/4) foot high. so no, of steps = 9/(3/4) = 12 =========suff.
St.2 Each step is is 1 foot wide.
width of stair don't solve the problem.... as we want height ....=========insuff.

Ans. A

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