Jump to content
Urch Forums

solving w/o calculating?


infinityzero

Recommended Posts

Is there a way to do this problem using logic and avoiding calculations, especially when running out of time? It'd be much appreciated. Thanks.

 

The 1992 census found that city A had 18% fewer residents than city B. The 1994 census found that city A's population grew by 18% over 1992, while city B's population had remained the same.

 

Col A: population of city A in 1994

 

Col B: population of city B in 1994

 

 

 

Ans: B

Link to comment
Share on other sites

u dont need to calculate since in 1992 pop. of B is higher A is lower to reach B's pop A's pop. should increase more than %18 this is because if B's pop is 100 A's is 82 18% of 100 is 18 but 18% of 82 is lesser so A's pop in 1994 is not 100 so the answer is B
Link to comment
Share on other sites

If 72.42 = k(24+n/100) where k and n are positive integers and n

 

17

16

15

14

13

 

another problem:

 

Y X 7 + 6 Y = Y 7 X

 

In the sum above ,if X and Y each denote one of the digits from 0 to 9 inclusive then X =

 

9

5

2

3

1

0

Link to comment
Share on other sites

If 72.42 = k(24+n/100) where k and n are positive integers and n

 

17

16

15

14

13

 

another problem:

 

Y X 7 + 6 Y = Y 7 X

 

In the sum above ,if X and Y each denote one of the digits from 0 to 9 inclusive then X =

 

9

5

2

3

1

0

 

7242=2400k+kn

 

k=3

kn=42

n=14

k+n=17

 

YX7

+6Y

---

Y7X

 

 

x=0

y=3

 

107

+63

---

170

Link to comment
Share on other sites

how u solved this problem ? Please explain.

 

Another question about ur solution : ur sum shd be 370 instead of 170 as ur taking y =3 ?

 

sorry you r right

 

first clue is that there is no carry from tens to hundreds

 

if we look only tens

 

X

6

-

7

 

i thought at first X can be 1 if it is 1 then

 

if we look at unit digits

 

7

Y

-

1

 

so Y is either -6 or 4 but if it is 4 then there is a carry so the whole calculation is wrong then

 

I thought let X be zero I didnt tried numbers greater than 1 since if I had used it the same scenario occurs as it occured with X=1

 

so X=0

 

by looking tens

 

X

6

-

7

 

since X=0 there should be a carry from unit digits

 

 

7

Y

-

0

 

so Y can be -7 or 3 so naturally it is 3 then the sum becomes 10 one carry occurs it adds to tens then th whole calculation is correct

Link to comment
Share on other sites

Thanks a lot , hace

 

 

sorry you r right

 

first clue is that there is no carry from tens to hundreds

 

if we look only tens

 

X

6

-

7

 

i thought at first X can be 1 if it is 1 then

 

if we look at unit digits

 

7

Y

-

1

 

so Y is either -6 or 4 but if it is 4 then there is a carry so the whole calculation is wrong then

 

I thought let X be zero I didnt tried numbers greater than 1 since if I had used it the same scenario occurs as it occured with X=1

 

so X=0

 

by looking tens

 

X

6

-

7

 

since X=0 there should be a carry from unit digits

 

 

7

Y

-

0

 

so Y can be -7 or 3 so naturally it is 3 then the sum becomes 10 one carry occurs it adds to tens then th whole calculation is correct

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...