Unit 2: 1. Fraction is multiplied by fraction, numerator is multiplied by numerator, denominator is multiplied by denominator, and what can be reduced is reduced first and then multiplied.

2. The commutative law, associative law and distributive law of integer multiplication are also applicable to fractional multiplication.

3. Who is who's score is who multiplied by who.

4. Two numbers whose product is 1 are reciprocal.

Unit 3: 1. Dividing by a number that is not equal to 0 is equal to multiplying the reciprocal of this number.

2. Knowing the fraction of a number, finding this number is equal to dividing this number by a fraction.

3. Knowing how many fractions are more or less than a number is equal to dividing the more or less part by the unit 1.

4. The former term of the ratio is equal to the latter term.

Unit 4: 1. The line segment connecting the center of the circle and any point on the circle is called radius. The line segment passing through the center of the circle with both ends on the circle is called the diameter.

2. Radius =r, diameter =d, C=πd=2πr, S=πr*, ring S=π(R*-r*).

Unit 5: 1. Percent means the percentage of one number to another, and percentage is also called percentage or percentage.

2. Knowing how much more or less than a number is equal to dividing the more or less part by the unit 1.

3. A discount means a few tenths, that is, a few percent.

4. Taxable amount = turnover x tax rate interest = principal x interest rate x time

There's no point in the back