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Giải câu 4 trang 55 sách toán VNEN lớp 4 tập 2

1 Đánh giá

Câu 4: Trang 55 sách VNEN toán 4

Tính bằng hai cách:

a. $\frac{5}{24}\times \frac{5}{12}\times 24$

b. $\left ( \frac{1}{4}+ \frac{2}{3} \right )\times \frac{4}{5}$

c. $\frac{3}{7}\times \frac{16}{33}+\frac{16}{33}\times \frac{4}{7}$

Bài làm:

a. $\frac{5}{24}\times \frac{5}{12}\times 24$

C1: $\frac{5}{24}\times \frac{5}{12}\times 24=\left ( \frac{5}{24}\times \frac{5}{12}\right )\times 24=\frac{25}{288}\times \frac{24}{1}=\frac{600}{288}$

C2: $\frac{5}{24}\times \frac{5}{12}\times 24=\frac{5}{24}\times \left ( \frac{5}{12}\times \frac{24}{1}\right )=\frac{5}{24}\times \frac{120}{12}=\frac{600}{288}$

b. $\left ( \frac{1}{4}+ \frac{2}{3} \right )\times \frac{4}{5}$

C1: $\left ( \frac{1}{4}+ \frac{2}{3} \right )\times \frac{4}{5}=\left ( \frac{3}{12}+\frac{8}{12} \right )\times \frac{4}{5}=\frac{11}{12}\times \frac{4}{5}=\frac{44}{60}$

C2: $\left ( \frac{1}{4}+ \frac{2}{3} \right )\times \frac{4}{5}=\frac{1}{4}\times \frac{4}{5}+\frac{2}{3}\times \frac{4}{5}=\frac{4}{20}+\frac{8}{15}=\frac{12}{60}+\frac{32}{60}=\frac{44}{60}$

c. $\frac{3}{7}\times \frac{16}{33}+\frac{16}{33}\times \frac{4}{7}$

C1: $\frac{3}{7}\times \frac{16}{33}+\frac{16}{33}\times \frac{4}{7}=\frac{48}{231}+\frac{64}{231}=\frac{112}{231}$

C2: $\frac{3}{7}\times \frac{16}{33}+\frac{16}{33}\times \frac{4}{7}=\left ( \frac{3}{7}+\frac{4}{7} \right )\times \frac{16}{33}=\frac{7}{7}\times \frac{16}{33}=\frac{112}{231}$

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Cập nhật: 07/09/2021

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