The expansion problem of mathematics improvement in grade five

Such problems are best solved by equations.

Let the primitive be x/y.

According to the meaning of the question: x/(y+2)

7/9

x/(y+3)

3/4

Proportional formula: 7y+ 14=9x.

3y+9

=4x

6y+ 18=8x

x=y-4

3y+9=4y- 16

2 1

If you don't use equations, you can think like this.

Molecules are immutable, so we must first make them the same, that is, find the least common multiple of molecules.

7/9

2 1/27

3/4

2 1/28

Combined with the meaning of the question, the original score can be calculated as

2 1/25

If you can't solve a system of binary linear equations, solve it. It feels simple, but it's hard to think of.