Aptitude - Alligation or Mixture - Discussion

Hello, According to alligation rule the answer is wrong. But I referred some books, I came to know that when in the question we gave the same kind of products like (first kind of rice and second of rice as given in the above question).
We should take the allegation rule as per question sequence.

In the above question, we have the highest value 7.20 first followed by 5.70. So we should take 7.20 first in alligation rule.

Hope my answer is helpful.

Details solution:

Let, X kg mixture with take 7.20 and 1 kg mixture with take 5.70.

Then, Cost price of 1 kg mixture is (7.20x + 5.70)/(x+1).

According to the question:

(7.20x + 5.70)/(x+1) = 6.30.

=> 7.20x + 5.70 = 6.30x + 6.30.

=> 0.90x = 0.60.

=> x = 2/3.

As per alligation rule they have written in wrong order.

7.20(x)+5.70(y)/x+y = 6.30.

Here x and y are the ratio's in which they are mixed.

7.20(x)+5.70(y) = 6.30(x)+6.30(y).

On solving we get x:y = 2:3.

This is the easiest method for these kind of problems.

Guys following rule of alligation we will get 3:2 (Cheaper quantity:Dearer quantity) as answer but in question it is asked the ratio of dearer qty to the cheaper one tats why answer will be 2:3 hope I have made my point clear!

No its 2:3 only.
How it comes is that,

-> (6.30-7.20)=> -0.60.
-> (5.70-6.30)=> -0.90.

Upon equating them acc to allegations rule, you get,
0.2:0.3 which will be 2:3;

I guess it comes this way..am I right?

Let the ratio be x/1-x
Then
7.20 (1-x) + 5.70 x = 6.30
7.20 -7.20x + 5.70x =6.30
7.20-1.50x =6.30
7.20-6.30 /1.50 =x
0.90/1.50 = x
3/5 =x
1-x = 1-3/5 =2/5
x/1-x = 3/5 /2/5 = 3/2

According to books cheaper price shoul b taken firtt then dearer. So I think answer is 3:2. Please clear my doubt m I right?

How 630 came?

According to the formula the cheaper price is came frist and bearer price is second. so according to me the answer is 90:60=3:2
am i right?