GMAT Problem Solving Discussions

[sachin_h]

Originally Posted by ajayreddy

191.
consider the cuboid...u hv three diff. rectangles - 6x8, 8x10 and 6x10 tht form the faces of the cuboid...if the cylinder rests on the 6x8 rectangle, then the max. diameter it can hv is 6 inches and max. height is 10 inches..hence volume = 90pi
when u consider 8x10 face, max dia = 8 in. and max vol = 96pi
when u consider 6x10 face, max dia = 6 in. and max vol = 72pi
hence, max vol = 96pi when dia = 8 in. i.e. radius = 4 inches

196.
missing data - ratio of soap:alcohol:water = 2:50:100

whenever a ratio is doubled or halved, u double or halve the first quantity of the ratio.
hence, soap:alcohol = 4:50
soap:water = 1:100
since it contains 100 cc of alcohol, amt. of soap = 8 cc. hence amt. of water = 800 cc.

220.

both were given x dollars in advance. let us assume their hourly wage be 'a' dollars.
thus, if john worked for 10 hrs, he shud get 10a dollars and mary shud get 8a dollars.
now, mary gave y dollars to john. hence, amt. left with mary = x-y. this is equal to the total wage tht she gets
therefore x-y = 8a
john gets x+y dollars. thus x+y = 10a
solving both the equations, u get x=9y.

234.

since we need to find only how many red beans were removed, we need to find hw many times 7 occurs as a factor of 147000...
147 = 49x3 = 7x7x3
thus, there were 2 red beans removed.

23_.

consider pt.P.. within the range -4 to 5 for x co-ordinate, it can have 10 values...similarly, for y co-ordinate, it can have values frm 6 to 16 i.e. 11 values...thus a total of 110 possible co-ordinate values.
now, R will hv the same y co-ordinate as P...hence, y co-ordinate of R can have 9 values (1 value is already assigned to P amongst the original 10 values)
similarly, Q will hv same X co-ordinate.hence, Q can have 10 values for x co-ordinate.
thus, total no. of triangles = 110 x 9 x 10 = 9900...i think this is the right answer and not 110...plz tell me if i am right or wrong...

Thanks a lot...
Yes, the answer for last question is 9900..A typo error from my side...
Regarding Q. 220, I had thought that the hourly wages for Mary and John are different...
The question mentions "If Mary gave John y dollars of her payment so that they would have received the same hourly wage"
I thought that they wud be receiving different hourly wages....

[ajayreddy]

Originally Posted by sachin_h

Thanks a lot...
Yes, the answer for last question is 9900..A typo error from my side...
Regarding Q. 220, I had thought that the hourly wages for Mary and John are different...
The question mentions "If Mary gave John y dollars of her payment so that they would have received the same hourly wage"
I thought that they wud be receiving different hourly wages....

well, thts the fine line between sums that seem 'tough' and sums that are 'easy'..u just need to CRACK THE CODE!!! ..

[lizzymcguire]

Hi guys

Please help me with this one from one of the maths tests from 800 score.com...
I am not convinced by the explanation in the test.

model | 2003 | 2004
--------|--------------------------------
A | 190 | 125
B | 200 | 205
C | 210 | 220

the table above shows quantities of cell phones by a retailer.
Assuming that prices did not change in 2003 and 2004, was the total revenue in 2004 greater than the revenue in 2003.
a) A is the most expensive phone
b) C is the least expensive phone

[ajayreddy]

Originally Posted by lizzymcguire

Hi guys

Please help me with this one from one of the maths tests from 800 score.com...
I am not convinced by the explanation in the test.

model | 2003 | 2004
--------|--------------------------------
A | 190 | 125
B | 200 | 205
C | 210 | 220

the table above shows quantities of cell phones by a retailer.
Assuming that prices did not change in 2003 and 2004, was the total revenue in 2004 greater than the revenue in 2003.
a) A is the most expensive phone
b) C is the least expensive phone

answer is A....cuz see, if u use statement 1 alone, u know A is the most expensive phone..so the prices of B and C are less than A...also, the quantities of both B and C have increased in 2004 by 5 and 10 units resp...but the quantity of A has decreased by 65 units...since A is the most expensive, we can conclude that the loss is greater than the profits made by B and C...hence st.1 is sufficient

st.2 is not sufficient because even though C is least expensive, u dont know which among A and B is more expensive..suppose A costs 10 rs. and B costs 200 rs., then the revenue in 2004 is greater..but if A costs more than B, then the revenue of 2003 is more...

[lizzymcguire]

hey thanks ajay!

[ajayreddy]

Originally Posted by lizzymcguire

hey thanks ajay!

no probs..the next time u want to thank sumone, just use the THANKS button below the post!!

[cyndrella]

How many times will the number 7 be written when listing the integers from 1 to 1000?

1) 110
2) 111
3) 271
4) 300
5) 304

[ajayreddy]

Originally Posted by cyndrella

How many times will the number 7 be written when listing the integers from 1 to 1000?

1) 110
2) 111
3) 271
4) 300
5) 304

from 1-10, there's only one 7...similarly, frm 11-20, 21-30,....91-100, except frm 71-80, there is one 7 in each set..tht makes a total of 9...frm 71-80, there are 10 sevens,....hence, total no. of seven's frm 1-100 = 19...similarly, frm 101-200, 201-300, 301-400....901-1000, except 701-800, there are 19x8 = 152 sevens...
frm 700-800, there are 19 + 100(no. of sevens in hundreds place) = 119 sevens...thus, total no. of sevens = 271

answer is C

[sharkon]

Originally Posted by ajayreddy

from 1-10, there's only one 7...similarly, frm 11-20, 21-30,....91-100, except frm 71-80, there is one 7 in each set..tht makes a total of 9...frm 71-80, there are 10 sevens,....hence, total no. of seven's frm 1-100 = 19...similarly, frm 101-200, 201-300, 301-400....901-1000, except 701-800, there are 19x8 = 152 sevens...
frm 700-800, there are 19 + 100(no. of sevens in hundreds place) = 119 sevens...thus, total no. of sevens = 271

answer is C

Ajay is there a way where we can use permutations and combinations to reach this result.

[cyndrella]

please answer this...my doubt...should consecutive numbers always be considered from lower to higher or the other way round is also possible?