Giải câu 4 trang 131 toán tiếng anh lớp 4

01 Đề bài:
 
Câu 4: Trang 131 sgk toán tiếng Anh lớp 4
Simplify then calculate:
Rút gọn rồi tính:
a)\(\frac{3}{15}-\frac{5}{35}\); 
b)\(\frac{18}{27}-\frac{2}{6}\);
c)\(\frac{15}{25}-\frac{3}{21}\); 
d)\(\frac{24}{36}-\frac{6}{12}\)
02 Bài giải:
 
a)Simplify:
Rút gọn
\(\frac{3}{15}\)= \(\frac{3 : 3}{15 : 3}\)= \(\frac{1}{5}\) 
\(\frac{5}{35}\) = \(\frac{5 : 5}{35 : 5}\) = \(\frac{1}{7}\)
Subtract two fractions:
Trừ hai phân số:
\(\frac{3}{15}-\frac{5}{35}= \frac{1}{5}-\frac{1}{7}= \frac{1 \times 7}{5 \times 7}-\frac{1 \times 5}{7 \times 5} = \frac{7}{35}-\frac{5}{35}=\frac{2}{35}\)
b) Simplify:
Rút gọn;
\(\frac{18}{27}\)= \(\frac{18 : 9}{27 : 9}\)= \(\frac{2}{3}\)
\(\frac{2}{6}\)= \(\frac{2 : 2}{6 : 2}\)= \(\frac{1}{3}\)
Subtract two fractions:
Trừ hai phân số:
\(\frac{18}{27}-\frac{2}{6}= \frac{2}{3}-\frac{1}{3}=\frac{1}{3}\)
c) Simplify:
Rút gọn:
\(\frac{15}{25}\) = \(\frac{15 : 5}{25 : 5}\) = \(\frac{3}{5}\)
\(\frac{3}{21}\) = \(\frac{3 : 3}{21 :3}\) = \(\frac{1}{7}\)
Subtract two fractions:
Trừ hai phân số:
\(\frac{15}{25}-\frac{3}{21}= \frac{3}{5}-\frac{1}{7}= \frac{3 \times 7}{5 \times 7}-\frac{1 \times 5}{7 \times 5}= \frac{21}{35}-\frac{5}{35}=\frac{16}{35}\)
d) Simplify:
Rút gọn:
\(\frac{24}{36}\) = \(\frac{24 : 12}{36 : 12}\) = \(\frac{2}{3}\)
\(\frac{6}{12}\)= \(\frac{6 : 6}{12 : 6}\)= \(\frac{1}{2}\)
\(\frac{24}{36}-\frac{6}{12}= \frac{2}{3}-\frac{1}{2}= \frac{4}{6}-\frac{3}{6}=\frac{1}{6}\)