Cant understand this math. someon eplz solve.

[godhuli_golpo]

a wall with no windows 11 feet high and 20 feet long. a large roll of wallpaper costs $25 and will cover 60 square feet of wall. A small roll of wallpaper costs $6 and will cover 10 square feet of wall. What is the least cost for enough wallpaper to cover the wall?

[vinay1983]

Assuming the wall to be a rectangle, the total area is 11*20=220 sq.ft.

The larger wall paper costs $25 to cover 60 sq.ft, so it costs (220*25)/60 = approx $ 88 to cover the wall.

The smaller wall paper covers 10 sq. ft @ $6, so the area to be covered is 22 times, hence the cost will be 22*6 = $ 132.

So, I feel the least cost has to be approx $ 88.

What is the source and the OA?

[sanjoy18]

Total sq ft= 11*20 =220 sqft
for large roll..cost per sqft= 25/60
for small roll it is 6/10
To cover up, lets consider larger roll required for x sqft wall and small roll require y sq ft wall
lest also consider Z is the cost

hence Z= (25/60)*x + (6/10)*y where x+y=220
z= [25*x+36*y]/60
for least cost we need to minimize z..
to do that we need larger value of x than the value of y (as co-efficient of x less than that of y)
hence x must be greater than 110.
now 60*z= 25*x + 36(220-x)= 36*220 -11*x
z= 132 -11*x/60
z= 132- 11*180/60
z=99
hence 99

[why i chose x=180 sqft...means 3 large roll..reason is also to minimize cost
if i had cover the 220 sqft wall using large roll it would cost 25*4=100 which greater than 99..so actually I used 3 large roll cost 25*3=75 and 4 small roll cost 4*6=24..hence total cost 75+24=99]

[sanjoy18]

Assuming the wall to be a rectangle, the total area is 11*20=220 sq.ft.

The larger wall paper costs $25 to cover 60 sq.ft, so it costs (220*25)/60 = approx $ 88 to cover the wall.

The smaller wall paper covers 10 sq. ft @ $6, so the area to be covered is 22 times, hence the cost will be 22*6 = $ 132.

So, I feel the least cost has to be approx $ 88.

What is the source and the OA?

Vinay1983..

it is not $88..it actually cost $100. as when you covered 220 sqft wall using large roll..You are actually using 4 large roll.So cost will be 25*4=$100..But actual answer would be $99 ..see my post .

[ikaplan]

You should assume that you can not split a large roll into smaller pieces. In order to cover the total wall area is 220 sq. ft you need 3 large rolls and 4 small rolls.

3* $25= $75
4* $6= $24

total $99

[vinay1983]

Assuming the wall to be a rectangle, the total area is 11*20=220 sq.ft.

The larger wall paper costs $25 to cover 60 sq.ft, so it costs (220*25)/60 = approx $ 88 to cover the wall.

The smaller wall paper covers 10 sq. ft @ $6, so the area to be covered is 22 times, hence the cost will be 22*6 = $ 132.

So, I feel the least cost has to be approx $ 88.

What is the source and the OA?

Vinay1983..

it is not $88..it actually cost $100. as when you covered 220 sqft wall using large roll..You are actually using 4 large roll.So cost will be 25*4=$100..But actual answer would be $99 ..see my post .

Yep I realised it late enough.It necessarily has to be a combi of paper rolls, only then can we acheive the desired outcome.

[Java_85]

IMO 99$ it is.

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Hi godhuli_golpo,

This question doesn't have the "style" or wording of a GMAT question. What is the source? In addition, you would have 5 answers to work with, which could help you to catch or avoid a math mistake and/or help you to estimate the correct answer. Can you include those answer choices?

GMAT assassins aren't born, they're made,
Rich

[godhuli_golpo]

To all,
I got this math from a bank job test. correct answer is given $99.

[ganeshrkamath]

a wall with no windows 11 feet high and 20 feet long. a large roll of wallpaper costs $25 and will cover 60 square feet of wall. A small roll of wallpaper costs $6 and will cover 10 square feet of wall. What is the least cost for enough wallpaper to cover the wall?

$25 for 60 square feet of wall, $6 for 10 square feet of wall.

We have to divide the given area into 60 sq.ft. and 10 sq.ft.

Total area = 11*20 = 220
220 = 3*60 + 4*10

Cost = 3*25 + 4*6 = 75 + 24
= [spoiler]$99[/spoiler]

Cheers