"We cannot solve our problems with the same thinking we used when we created them."
- Albert Einstein
6.
The ratio of the number of boys and girls in a college is 7 : 8. If the percentage increase in the number of boys and girls be 20% and 10% respectively, what will be the new ratio?
[A].
8 : 9
[B].
17 : 18
[C].
21 : 22
[D].
Cannot be determined
Answer: Option E
Explanation:
Originally, let the number of boys and girls in the college be 7x and 8x respectively.
Their increased number is (120% of 7x) and (110% of 8x).
K.Kiran Kumar said:
(Wed, Aug 4, 2010 12:52:08 AM)
I can not get that how 120% of 7x and 110% of 8x.
Please someone explain it.
Ramesh said:
(Thu, Dec 9, 2010 06:30:45 AM)
7:8 can also be written as 70:80
120/100*70 = 84
110/100*80 = 88
so,new ratio= 84 : 88
or 42 : 44
or 21 : 22
Abhinesh said:
(Wed, Jan 12, 2011 02:21:42 AM)
(7x+0.2*7x)/(8x+0.1*8x)=21:22
Sripal S said:
(Sun, Mar 6, 2011 11:56:26 AM)
@Kiran Kumar
note that something we included to get 20%
For example the ratio of the ratio of to boys ages was 5:2
we can write it as 5x : 2x we get exact ratio we will not consider it alone
For that way 7x 8x will appear
then
to covert 20% into no. it will be 20/100
note that the unknown was x
then 20/100x*x
so we take common one x(20/100+1)
so x(20/100+100)
x(120/100)
that was we get 120/100
forget x because that x which is in 7x both are same so we get 120/100*7x
Sasha said:
(Fri, May 6, 2011 10:31:27 PM)
I like ramesh's methods ! thanks a lot :).
Poonma said:
(Tue, Jun 14, 2011 04:00:10 AM)
Ramesh your to good.
Khushboo said:
(Tue, Jul 19, 2011 11:52:34 AM)
Why do we multiply 120% by 7x and 100% by 8x
Why not we simply multiply 20% by 7x and 10% by 8x ?
Please someone explain me.
Raj said:
(Tue, Aug 9, 2011 01:05:55 PM)
RAMESH very well said. ! keep posting your SHORTCUT method. Its very useful for us. !i search at every discussion. Because of you. !
Priyabrata said:
(Mon, Sep 26, 2011 06:32:31 AM)
20% of 7=14/10,total increase 7+14/10=84/10
10% of 8=8/10,total increase 8+8/10=88/10
now compare ratio of Boys and Girls
84/10:88/10
or 84:88
or 42:44
or 21:22
Kavya said:
(Thu, Sep 29, 2011 04:24:32 PM)
I am getting 7:4 by whichever method I do. I am not satisfied with any explanations given. Help me.
Rajeev said:
(Tue, Nov 8, 2011 05:21:42 PM)
@ ramesh
Can you tell you multiply 70 & 80 instead of 7 & 8, as we get same answer in both the cases?
The required ratio =