Ratio and proportion - HEEEEELLLLPP

[lazykidarr]

Hi!
I don't have ANY IDEA on how to do ANY kind of math problem coz i am not a math student but i have to do some QA questions for my entrance exams so I need a little bit of help here!
so...here's the question:-

The monthly incomes of A and B are in the ratio 8:7 and those of B and C are in the ratio 5:3. If the monthly income of C is Rs.3,360, find the monthly income of A.

Options:
a) Rs.3500
b) Rs.4200
c) Rs.5600
d) Rs.6400
I tried solving the problem and I can't get the answer in more than 3 digits! Desperately need help here!

 

[HallsofIvy]

A ratio is a fraction and proportion is a statement that two fractions are equal. Here you are told that A/B= 8/7 and that B/C= 5/3. From the first equation, multiplying both sides by 7B, 7A= 8B. Dividing both sides by 8, B= (7/8)A. Doing the same with the second equation, 3B= 5C, B= (5/3)C. So B= (7/8)A= (5/3)C. Multiply both sides by 8/7 to get A= (8/7)(5/3)C= (40/21)C. Since C= 3,360, A= (40/21)(3360). I don't understand what you mean by "more than 3 digits". It just simple arithmetic. Are you allowed to use a calculator? Even without a calculator it is easy to see that 3360 is divisible by 3: 3360/3= 1120 so 3360/21= 1120/7 and, remarkably, 1120/7= 160. Can you multiply 40(160)?

And this surely does not belong in "Calculus and Beyond". It is, as I said, simply arithmetic.

 

[Architeuthis Dux]

Hi there,

Don't worry, solving ratio and proportion problems can be tricky for those who are not comfortable with math. Let me walk you through the steps to solve this problem:

1. Write down the given ratios: A:B = 8:7 and B:C = 5:3
2. We know that the monthly income of C is Rs.3,360, so we can write the ratio B:C as 5:3360/3 = 5:1120
3. Now, we need to find the ratio A:B in terms of C. To do this, we need to find the common factor between 7 and 1120, which is 7. Dividing both numbers by 7, we get A:B = 8:7 and B:C = 5:160
4. Since we have the ratios A:B and B:C, we can combine them to get the ratio A:C = 8:7 x 5:160 = 8:32
5. We know that the monthly income of C is Rs.3,360, so we can write the ratio A:C as 8:3360/32 = 8:105
6. Finally, we can solve for A by setting up a proportion: 8/105 = x/3360, where x represents the monthly income of A. Solving for x, we get x = Rs. 2560.

Therefore, the monthly income of A is Rs. 2560. I hope this helps and good luck with your entrance exams! Remember, practice makes perfect.