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Let the production rate of standard loom and industrial loom be x & y fabric rolls / hour. Let y/x = k

The number of fabric rolls to be produced = 14(7x + 5y)
The number of hours taken by 6 industrial looms = 14(7x+5y)/6y = 7(7x+5y)/3y = 7/3 (7x/y +5) = 7(7/k + 5)/3
The number of hours taken by 21 standard looms = 14(7x+5y)/21x = 2/3 (7 + 5y/x) = 2(7+5k)/3
2(7+5k)/3 - 7(7/k + 5)/3 = 14
(14 + 10k) - (49/k + 35) = 42
10k - 49/k = 42 + 35 - 14 = 63
10k^2 - 63k - 49 = 0

k = 7 or -0.7
k = 7 since -0.7 is not feasible since production rates are +ve.

The ratio of production rate of one industrial loom to the production rate of one standard loom = 7

IMO D
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Let, rate of 1 standard loom=a & rate of 1 industrial loom=b
7a+5b can do the work in 14 hours.
W=14(7a+5b)

6b working alone can do job in 14 hours less time than 21a working alone.
W/6b = W/21a -14 ........(Put W=14(7a+5b))
98a+70b/6b = 98a+70b/21a -14
21a(7a+5b)=6b(5b-14a)
49a^2 +63ab-10b^2 =0
Let, x=b/a
10x^2 -63x -49=0
x= [-(-63)+-(63^2 -4*10*(-49))^1/2 ]/2*10
x= [63+-(5929)^1/2]/20
x=(63+-77)/20
x= 63-77/20=-14/20....Not possible
x= 63+77/20 =140/20=7

D. 7
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7s+5i
w=14(7s+5i)

6it=21s(t+14)
w=6it

6it=14(7s+5i)
6it=21s(t+14)
r=i/s

21(t+14)=14(7+5r)

3t=10r-28

6rt=14(7+5r)

we get t ki value --10r-28/3

substitute T in the eq

20r^2-126r-98

(2r+1) (5r-9)

r=49/5
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Let rate of industrial loom be I ; Standard loom be S; Work to be done be W

Given : W / (5I + 7S) = 14

Also given : W/21s - W/6I = 14

The solving is long, answer comes to I/S = 7:1

7 is the answer.
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Here's my solution for this question
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Let s and i be the constant rates of the standard and industrial loom respectively.

Given, 7/s + 5/i = 1/14
and, 6/i = 21/s - 1/14
Solving the above two we get, i/s = 7:1

Answer is D
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S is rate of standard loom
I is rate of inductrial loom
W is total work

7 standard looms and 5 industrial looms finish job in 14 hours
W = 14 ( 7S + 5I)

6 Industrial alone W/6I
21 standard looms alone W/21S

Industrial loom finish 14 hours sooner so
W/6I = W/21S -14

substitute W= 14 (7S + 5I)

14(7S + 5I) / 6I = 14 (7S +5I) /21S -14
divide everything by

7S + 5I/ 6I = 7S + 5I /21S -1

Since 7S + 5I /21S -1 = 7S + 5I -21S/21S = 5I -14S / 21S

we have 7S + 5I/ 6I = 5I -14S/21S

Let Ratio be I/S

Therefore
7 +5R/6R = 5R -14 / 21

Cross multiple 21(7+5R) = 6R(5R-14)

147 + 105R = 30R^2 - 84R
30R^2 - 189R -147 =0

divide by 3
10R^2 -63R -49 = 0

(10R +7) ( R-7) =0
only positive is R =7

Therefore answer D R=7
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i am going with option d.
s = rate of 1 SL, i = rate of 1 IL, w = total job size.
ratio of IL/SL, r = i/s
total job - combined rate x time = w = 7s+5i x 14.
as i = rs, 14(7s+5rs) = 14s(7+5r)
time for 21SL - time for 6IL = 14 hours.

now to check for d if it is correct, s=1, i=7
7SL = 7 and 5IL = 5x7 = 35, combined = 42
14hrs to finish, 42x14=588 units
time for SL = 588/21 = 28hrs
time for IL = 588/42 = 14hrs, diff = 28-14 = 14.
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let:
a= production rate of one standard loom
b= production rate of one industrial loom
total work = 1 job

equation 1
7 standard looms + 5 industrial looms finish job in 14 hours

7a+5b=1/14

equation 2
6 industrial looms alone take 14 hours less than 21 standard looms alone

time for 21 standard
1/21a


time for 6 industrial
1/6b



1/6b=1/21a-14

let r = b/a

a= 1/14(7+5r)

1/6rb=1/21b-14

1/b=14(7+5r)



14(7+5r)/6r=14(7+5r)/21-1

7+5r/6r=5r-14/21

21(7+5r)=6r(5r-14)

147+105r=30r^2-84r
30r^2-189r-147=0
10r^2-63-49=0
(10r+7)(r-7)=0

r=7

a/b=7


Bunuel
A textile workshop must produce a certain number of identical fabric rolls. The workshop has standard looms and industrial looms. Each standard loom produces fabric at the same constant rate, and each industrial loom produces fabric at the same constant rate. If 7 standard looms and 5 industrial looms, working together, can complete the job in 14 hours, and 6 industrial looms working alone can complete the job in 14 hours less time than 21 standard looms working alone, what is the ratio of the production rate of one industrial loom to the production rate of one standard loom?

A. 3
B. 5
C. 6
D. 7
E. 9


 


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according to the question 7s+5i ==> 14 hours
6i ===> 14 hours
now we need i/s =?
note that the amount of work done in both cases is same hence we can equate them
6i *14 = 14*(7s+5i)
hence solving this we will get i =7s
ti.e i/s = 7
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7s+5i=1/14 ...e1
(1/21s-1/6i)=14 ....e2
we need i/s

we need to pluggin i/s=9 so i=9s substituting for i in equ1 and 2 we get 52s=1/14 or s=1/52*14
Eq2: 1/21s-1/54s=14 s=1/14*21*18 ...s value not matching so reject...

use 7 i/s=7 subtituting for i, in both eq we get s=1/42*14 so this is the right answer

solving for these we get
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One standard loom = s
One industrial loom = i
Total job = W
Total time = 14 hours
Therefore, W = R x T = (7s + 5i) x 14
Let r = i/s or i = rs, W = 14s (7 + 5r)
21s can do alone = W/21s
6i can do alone = W/6i
6i can do less than 14 hours, which 21s can do, W/6i = (W/21s) - 14
14s (7 + 5r)/6 rs = 14s (7 + 5r)/21 s - 14
or, (7 + 5r)/6r = (7 + 5r)/21 - 1
or, (7 + 5r)/6r = (5r - 14)/21
From here, (10r + 7)(r - 7) = 0
Since there is no negative value, r = 7
Answer is (D)
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I am solving this problem by testing options.

Lets assume ,

the production rate of one standard loom =1
the production rate of one industrial loom = m

So, total work is ( 7.1+ 5.m ).14=14(7+5m)
now , the needed time for 21 Standard loom, a = 14.( 7+5m) / 21 .1 = 2(7+5m)/3
the needed time for 6 industrial loom , b = 14(7+5m)/6m= 7(7+5m)/3m

testing the options ;

when m= 3 , a = 2.(7+15)/3 = 14.6
b = 7.22/9 =17.1

a-b is not 14 . so option a is wrong .

when m =5 , a= 2.( 7+25)/3 = 21.33
b = 7.(7+25) = 14.93

as a-b is less than 14 , option b is also wrong

when m =6, a =2(7+30)/3=24.667
b =7.(7+30)/18 =14.38

option c is wrong .

when m =7, a =2.42/3 = 28
b= 7.42/21=14

here , a-b is clearly 14 . so 7 is the correct ans.

Right ans is option d.7
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let's say, standard loom working rate is "s" and industrial loom working rate is "i".
7s+5i = 1/14___(eq1)
As per question, 1/(21s) - 1/(6i) = 14____(eq2)

Multiply eq 1 & 2, we will get

7/21 - 7/6(s/i) + 5/21(i/s) - 5/6 = 1
1/3-5/6 - 7/6(s/i) + 5/21 (i/s) = 1
5/21(i/s) - 7/6 (s/i) = 3/2 ____(eq3)

Now we can check options for correct ratio of i/s which will satisfy the above (eq3)

Correct answer is 7. (D)
Bunuel
A textile workshop must produce a certain number of identical fabric rolls. The workshop has standard looms and industrial looms. Each standard loom produces fabric at the same constant rate, and each industrial loom produces fabric at the same constant rate. If 7 standard looms and 5 industrial looms, working together, can complete the job in 14 hours, and 6 industrial looms working alone can complete the job in 14 hours less time than 21 standard looms working alone, what is the ratio of the production rate of one industrial loom to the production rate of one standard loom?

A. 3
B. 5
C. 6
D. 7
E. 9


 


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for the GMAT World Cup Competition

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needed I/S

given -
7S + 5I = 1/14
=> 98S + 70I = 1 ----- eq1
also given
1/6I = 1/21S - 14 --------eq2

dividing eq1 by S on both sides

98 + 70 (I/S) = 1/S
let I/S = X
70X + 98 = 1/S

multiplying eq2 with S on both sides

1/(6X) = 1/21 - 14S
1/(6X) - 1/21 = -14 /(70X + 98)
(21 - 6X / 126X) * (70X + 98) = -14
(21 - 6X) (70X+98) = -1764X
2058 + 882X - 420X^2 = -1764X
2058 + 2646X - 420 X^2 = 0
420X^2 - 2646X - 2058 = 0
dividing by 2 -
210X^2 - 1323X - 1029 = 0
dividing again with 21
10 X^2 - 63X - 49 = 0

solving for X we get X = 7 or -14/20, as we see 7 in the answer options we can go for that
also, X cannot be negative, since it doesn't make sense for this question
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Let, r=i/s =?

7 standard looms and 5 industrial looms, working together, can complete the job in 14 hours.
Job= (7s+5i)*14 _____(1)

6 industrial looms working alone can complete the job in 14 hours less time than 21 standard looms working alone.
J/6i = J/21s -14 ____(2)
Put value of J from(1) in (2)
(7s+5i)14/6i = (7s+5i)14/21s -14
(7s+5i)/6i = (7s-5i)/21s -1
(put I=rs)
(7+5r)/6r = (7+5r)/21 -1
49+ 35r= 10r^2 -28r
10r^2 -63r -49=0
Solving it using quadratic formula we get, r= 63±77/20
r must be postive.
r= 63+77/20 = 140/20 = 7/1

D
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we have to find ratio of production rate , now what is ration its a fraction so if we say R(ratio)=i/s(industrial/standard) ---1

now they have given us important thing (7s +5i)*14=f(fabric roll)
now we need 1 and put that in above equation subsitute i (7s+5rs)*14 = f
take out s and solve
we will get f/14(7+5r)

no we also have given difference between the production rate and what we found above is exact that
so we continue to solve an get to equation
f/21s -f/6i=14
if we continue to solve at the end we will get to equation 10r^2-63r-49
and if we solve it we will get one real value that is 7 and thats answer
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