There are 2 packets of flour, Y & Z.The ratio of the mass of Y to Z is 4:1. If 26g is added to Z,the ratio of the mass of Y to Z is 7:5. Find the mass of the 2 packets at first. Pls show how to solve by model method as i have not learnt algebra. tks

let the mass of Y be 4x

let the mass of Z be x , (notice Y:Z = 4x:x = 4:1 )

new Z = x+26

now Y:Z = 7:5

4x/(x+26) = 7/5
20x = 7x + 182
13x = 182
x = 14
4x = 56

the two packets had a mass of 56 g and 14 g.

Here is the same question from an earlier date
http://www.jiskha.com/display.cgi?id=1313814541
Both drwls and I are giving you an algebraic solution, looking slightly different but in effect containing the same steps.
I don't think a curriculum should present questions when the proper tools have not been taught.
That would be similar to asking somebody to bake a cake, but saying you have to do it without having an oven.

I agree but my teachers don't care and even wrong answers have to be solved by ourselves and I keep getting them wrong again tks to both of you for your help

To solve this problem using a model method, we can create diagrams representing the packets of flour and the given information.

Let's start by representing the initial mass of Y and Z. Since the ratio of the mass of Y to Z is 4:1, we can draw four equal parts to represent Y and one equal part to represent Z.

Y: O O O O
Z: O

Next, we are told that 26g is added to Z. So, in our diagram, we can add another equal part to represent the additional 26g.

Y: O O O O
Z: O O

Now, we are given that the new ratio of the mass of Y to Z is 7:5. This means we need to divide each quantity into equal parts based on these ratios. We can divide Y into seven equal parts and Z into five equal parts.

Y: O O O O O O O
Z: O O O O O

From our diagram, we can count the number of parts in Y and Z.

Y: 7 parts
Z: 5 parts

Since the total number of parts for Y and Z combined is 12 (7 + 5), we can set up a proportion to find the mass of each part.

Total mass of Y and Z at first / Total number of parts = Mass of each part

Let's say the mass of each part is x. We can set up the proportion as follows:

Total mass at first / 12 = x

Now we can solve for the total mass at first. Rearranging the equation:

Total mass at first = x * 12

To determine the value of x, we need additional information.