Distributive law of multiplication 1 Find the value

Distributive law of multiplication

1. Find the value of both number sentences in each set and then discuss with your partner what you find. A. （6+4）× 5 = 6× 5+4× 5 B. （8+12）× 4 = 8× 4+12× 4 C. 10×（7+3） = 10× 7+10× 3

Example 1: There is a rectangular playground in a primary school , it is 70 meters long and 40 meters wide. After extending the playground, its width will be increased by 10 meters. Please find: 70 m 40 m 10 m The area of the playground after expansion. Hint: The area of a rectangle = length ×width

Example 1: There is a rectangular playground in a primary school , it is 70 meters long and 40 meters wide. After an extension, its width will be increased by 10 meters. Please find the area of the playground after expansion ? 70 m Way 1: （40+10） × 70 =50 × 70 =3500（m 2） 40 m 10 m Way 2: 40× 70+10× 70 How has it been calculated? =2800+700 =3500（m 2）

On sale The discount price of the jacket is £ 5. The discount price of a pair of trousers is £ 10. How much in total for 3 sets of jackets and trousers? 3 X(5+10) 3 X 5+3 X 10 =3 X 15 =15+30 =45£

Can you find more examples like this？ （40+10）× 70 ( ＋ )× = = 40× 70 + 10× 70 × ＋ × Distributive law of multiplication. The sum of two numbers multiplied by another number. We can multip the two addends by the number respectively and then add the two products. The result remains the same.

2. True or False? Show √ or × ①（28+16）× 7 ② 15× =28 × 7+16 × 7 39+45× 39（15+45)× = √ 39 √ √ = × 1 ③ 74×（20+1） 74× 20+74 ④ 5×（22+17）= 35× 22+17 × = 35× 22+35× 17 ⑤ 8×（11× 9）=8× 11× 8× 9 ×

3. Choose the right answer： 24× 12+24=（ C） A. 24×(12+24) B. 24× 12+24× 24 C. 24×(12+1)

（a + b）×c=a×c + b×c Solve each problem below by using the distributive law of multiplication （1） 125×（8+1） =125× 8+125× 1 =1000+125 =1125 （2）17× 73+17× 27 =17×(73+27) =17× 100 =1700 Use the distributive law of multiplication to make the calculation simpler.

Use the operation laws you have learned to calculate the answer efficiently 25× 24