Aptitude - Ratio and Proportion - Discussion

Discussion Forum : Ratio and Proportion - General Questions (Q.No. 6)
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?
8 : 9
17 : 18
21 : 22
Cannot be determined
Answer: Option
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).

120 x 7x and 110 x 8x
100 100

42x and 44x
5 5

The required ratio = 42x : 44x = 21 : 22.
5 5

Discussion:
61 comments Page 5 of 7.

Narayana Rao Gartam said:   1 decade ago
20% of 70 is 14 (20/100*70) So, Total increase is 84.
10% of 80 is 8 So, total increase is 88.

Ratio of 84/88 = 21/22,
i.e 21:22.

Md shahrukh said:   1 decade ago
Let the no of boys 7 and girls 8.

7x120/100: 8x110/100.

840:880.

So answer is 21:22.

Atul1487 said:   1 decade ago
Boys: Girls.
7:8.

20% increase in boys no. so,

7*20% = 1.4 so total boys = 7+1.4 = 8.4.

10% increase in girls.

8*10% = 0.8 So total Girls = 8+0.8 = 8.8.

So Ratio of Boys & Girls.
8.4 : 8.8.

21:22 Answer.

Stark Vin said:   1 decade ago
Hi all,

One minor doubt, why we are using for every question for ratio, what x mean? is a assumed value or what ? for this question if we didn't use x also we are getting the answer, but in other cases, we need to use X, please suggest me a good method.

Thanks.

Gowtham said:   1 decade ago
Simply find 20% of 7 and 10% of 8.

It will be 1.4 and 0.8 respectively.
Till this ok then,how 8.4:8.8.
And how to convert it into fraction.
So the ratio is 8.4:8.8.

Then convert the fraction into whole numbers.

If I multiply by 10 I will get 84:88 now we can easily simplify it.

So we get 21:22.

Nive said:   1 decade ago
Simply find 20% of 7 and 10% of 8.

It will be 1.4 and 0.8 respectively.

So the ratio is 8.4:8.8.

Then convert the fraction into whole numbers.

If I multiply by 10 I will get 84:88 now we can easily simplify it.

So we get 21:22.

Zahir said:   1 decade ago
20%of7 = 7/5 that means boys total = 7+7/5.

=42/5.

10%of8 = 4/5 that means girls total = 8+4/5 = 44/5.

Boys : Girls = 42/5:44/5.

=42:44.

=21:22.

Pankaj said:   1 decade ago
There is some problem to understand the problem ie question is asked 20% and 10% but here get 120% and 110% why ?

Sunali said:   1 decade ago
Thanks priyabhrt.

Prasanna said:   1 decade ago
@rajeev.

Yes you get the same answers.


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