Question

rút gọn rồi tính

a,2/5+9/15=

b,15/45+2/3=

c,28/32+45/72=

d,8/28+9/21=

 

Answer 1

a: =2/5+3/5=1

b: =1/3+2/3=1

c: =7/8+5/8=12/8=3/2

d: =2/7+3/7=5/7

Answer 2

\(a,\dfrac{2}{5}+\dfrac{3}{5}=\dfrac{5}{5}=1\\ b,\dfrac{1}{3}+\dfrac{2}{3}=\dfrac{3}{3}=1\\ c,\dfrac{7}{8}+\dfrac{5}{8}=\dfrac{12}{8}=\dfrac{3}{2}\\ d,\dfrac{1}{7}+\dfrac{3}{7}=\dfrac{4}{7}\)

Answer 3

a) 2/5+ 3/5= 5/5=1

b) 1/3+2/3=3/3=1

c) 7/8+5/8= 12/8=3/2

d) 2/7+3/7=5/7

 

Answer 4

a, \(\dfrac{2}{5}+\dfrac{9}{15}=\dfrac{6}{15}+\dfrac{9}{15}=\dfrac{15}{15}=1\)

b, \(\dfrac{15}{45}+\dfrac{2}{3}=\dfrac{1}{3}+\dfrac{2}{3}=\dfrac{3}{3}=1\)

c, \(\dfrac{28}{32}+\dfrac{45}{72}=\dfrac{7}{8}+\dfrac{5}{8}=\dfrac{12}{8}=\dfrac{3}{2}\)

d, \(\dfrac{8}{28}+\dfrac{9}{21}=\dfrac{2}{7}+\dfrac{3}{7}=\dfrac{5}{7}\)