Question

tính bằng cách thuận tiện nhất:

a).15/21+7/21+5/21

b).4/7+8/15+22/15

ai lảm nhanh đầy đủ mới tick

Answer 1

a) 15/21 + 7/21 + 5/21

= (15/21 + 5/21) + 7/21

= 20/21 + 7/21

= 27/21

b) 4/7 + 8/15 + 22/15

= 4/7 + 2

= 18/7

nha bn

Answer 2

a,\(\frac{15}{21}+\frac{7}{21}+\frac{5}{21}\)

= \(\left(\frac{15}{21}+\frac{5}{21}\right)+\frac{7}{21}\)

=  \(\frac{20}{21}+\frac{7}{21}\)

=\(\frac{27}{21}\)

b, \(\frac{4}{7}+\frac{8}{15}+\frac{22}{15}\)

=\(\frac{4}{7}+\left(\frac{8}{15}+\frac{22}{15}\right)\)

= \(\frac{4}{7}+2\)

= \(\frac{18}{7}\)