I have certain doubts about this one. Gurus can you please help?
In the rectangular solid, if AB=5, what is the surface area of the solid?
1. BC=8
2. The volume of the solid = 80
5-Day Free Trial
5-day free, full-access trial TTP
Available with Beat the GMAT members only code
MORE DETAILS
Surface Area of Rectangular Solid
This topic has expert replies
-
cubicle_bound_misfit
- Master | Next Rank: 500 Posts
- Posts: 246
- Joined: Mon May 19, 2008 7:34 am
- Location: Texaco Gas Station
- Thanked: 7 times
-
bluementor
- Master | Next Rank: 500 Posts
- Posts: 418
- Joined: Wed Jun 11, 2008 5:29 am
- Thanked: 65 times
Notation:
AB = a = 5
BC = b
CD = c
Surface area, S = 2ab + 2ac + 2bc
Volume, V = abc
Statement 1: b=8
We still don't know anything about c, hence insufficient.
Statement 2: V=80
abc = 80
5bc = 80
bc = 16
S = 2a(b + c) +2(16)
We still don’t know c, hence insufficient.
Both statements together:
Substitute b=8 into bc=16 to evaluate c. We can now work out the surface area, S. Sufficient. Choose C.
-BM-
AB = a = 5
BC = b
CD = c
Surface area, S = 2ab + 2ac + 2bc
Volume, V = abc
Statement 1: b=8
We still don't know anything about c, hence insufficient.
Statement 2: V=80
abc = 80
5bc = 80
bc = 16
S = 2a(b + c) +2(16)
We still don’t know c, hence insufficient.
Both statements together:
Substitute b=8 into bc=16 to evaluate c. We can now work out the surface area, S. Sufficient. Choose C.
-BM-
-
iwant700plus
- Senior | Next Rank: 100 Posts
- Posts: 33
- Joined: Thu Feb 19, 2009 7:19 pm
- Location: DC
- Thanked: 2 times
Surface area = 2lw+2lh+2hw = 2(lw+lh+hw)=2(5(w+h)+wh)
Let l=AB=5. What is w and h?
1) Let w=BC=8. Insufficient, no info about h.
2)V=lwh=80-->5wh->wh=16. While this gives us wh, it gives different values for w+h e.g 4*4=16, w+h=8 but for 2*8=16, 2+8=10. Insufficient.
Taken together
From stmt 1, we know w=8
So wh=16-->8h=16, h=2.
With all the dimensions, we can calculate surface area. Sufficient.
IMO, Ans is C
Let l=AB=5. What is w and h?
1) Let w=BC=8. Insufficient, no info about h.
2)V=lwh=80-->5wh->wh=16. While this gives us wh, it gives different values for w+h e.g 4*4=16, w+h=8 but for 2*8=16, 2+8=10. Insufficient.
Taken together
From stmt 1, we know w=8
So wh=16-->8h=16, h=2.
With all the dimensions, we can calculate surface area. Sufficient.
IMO, Ans is C
