Aptitude - Ratio and Proportion - Discussion

Let the boys be 7x and girls be 8x.

Boys 20 percent = 7x * 20/100 = 7X/5.
Girls 10 percent = 8x * 10/100 = 4x/5.
Total boys = 7X + 7x/5 = 42x/5.
Total girls = 8x+ 4x/5 = 44x/5.

So, ratio;

Total boys : total girls = 42x/5 /44x/5 = 22/22 = 21:22.

42/5 and 44/5 how is it 21 : 22? Please explain in detail.

Ramesh sir, how you get 42:44?

The ratio of the cost price and selling price is 4:5 what is the profit percentage?

Does anyone know how to solve this?

How you took ratio 21:22 from 42/5 : 44/5?

How 5 is eliminated? Please explain.

@Chaitra.

6 * 7 = 42 and 11 * 4 = 44.

Actually, I am getting answer as a
(120/100)*7=8.4 so approximately = 8.
(110/100)*8=8.8 so approximately = 9.

The answer is 8:9.

Given : B : G = 7:8.
This can be written as 7x : 8x ( X being the common multiplier).
Let x = 10 (For simple Calculation)
So Boys = 70 & Girls = 80.
Increased Of Boys by 20% = 70*20/100 = 14.
So After Increase boys would be = 70 + 14 = 84.
Similarly Girls = 80*10/100 = 8 & Girls After Increase would be = 80 + 8 = 88.

New Boys : New Girls = 84:88.
Simply 21:22.

The total percent of 7x is 100% and they increase 20% so we take it as 120*7x in the same way 110*8x is taken.

@Stark Vin.

We are taking X because ratio means dividing the total quantity into some parts and the number of parts we divide them into is represented in the form of the ratio.

For example, if I have 30 chocolates and if I want to divide them in the ratio 1:2 then first I will see into how many equal parts I need to divide the chocolates into that is 3 in this case why? Because ratio is 1:2 that is to parts I want is 3. That means I need to divide 30 into 3 equal parts and then take 1 part on one side and other part on the other side. This simply means if I divide 30 by 3 I get 10. This means I divided 30 into 3 equal parts where each part contains 10 chocolates. Now I need to divide them in the ratio 1:2 so I take 10 chocolate on one side which is one part of 30 in this example and remaining 2 parts which add up to 20 in other parts. Now 10 by 20 equals 1 by 2 or 1:2 that is what we call as ratio. That is ratio is the representation of total quantity in its simplest form. We could have written it as 10:20 by we need to simplify as much as possible so we take it as 1:2. Now coming to this question we have the boys to girls ratio as 7:8 that simply means the total strength was divide into 7+8 parts but since we do not know what is the total strength we take it as some variable say t now, t by 15 we assume as x. This means now I have divided total strength into 15 equal parts were each part contains x. In that 7x we take as number of boys and 8x as number of girls.