8/15 + 7/4 + 7/15 + 5/4

= 8/15 + 7/15 + 7/4 +5/4

= ( 8/15 + 7/15) + ( 7/4 + 5/4)

= 15/15 + 12/4

= 1 + 3

=4

=8/15+7/15+7/4+5/4

=1+3

=4

\(\dfrac{15}{8}\) : \(\dfrac{5}{20}\) - \(\dfrac{7}{8}\) : \(\dfrac{1}{4}\) 

= \(\dfrac{15}{8}\) : \(\dfrac{1}{4}\) - \(\dfrac{7}{8}\) : \(\dfrac{1}{4}\)

= ( \(\dfrac{15}{8}\) - \(\dfrac{7}{8}\)) : \(\dfrac{1}{4}\)

= \(\dfrac{8}{8}\) \(\times\) 4

= 4

Bài làm

   \(\frac{7}{15}x\frac{3}{8}+\frac{7}{15}x\frac{5}{8}\)

= \(\frac{7}{15}x\left(\frac{3}{8}+\frac{5}{8}\right)\)

= \(\frac{7}{15}x\frac{8}{8}\)

= \(\frac{7}{15}x1\)

= \(\frac{7}{15}\)

# Chúc bạn học tốt #

\(\frac{7}{15}\cdot\frac{3}{8}+\frac{7}{15}\cdot\frac{5}{8}\)

\(=\frac{7}{15}\cdot(\frac{3}{8}+\frac{5}{8})\)

\(=\frac{7}{15}\cdot1=\frac{7}{15}\)

\(\frac{7}{15}\times\frac{3}{8}+\frac{7}{15}\times\frac{5}{8}\)

\(=\frac{7}{15}\times\left(\frac{3}{8}+\frac{5}{8}\right)\)

\(=\frac{7}{15}\times1\)

\(=\).....................

Tự làm tiếp nhé!

b, 98,54- (41,82 - 35,72 ) 

=98,54 - 6,1

=92,44

a.8/15+7/4+7/15+5/4

=8/15+7/15+7/4+5/4

=15/15+12/4

=1+3=4

b.98,54-(41,82-35,72)

=98,54-6,1

=92,44

15/8-4/7+2-3/7=15/8-(4/7+3/7)+2=15/8+1+2=15/8+3=39/8

\(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)

\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)

\(=\frac{5}{15}+\frac{12}{18}\)

\(=\frac{1}{3}+\frac{2}{3}\)

\(=\frac{3}{3}=1\)

\(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)

\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)

\(=\frac{1}{3}+\frac{2}{3}\)

\(=1\)

\(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)

\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)

\(=\frac{5}{15}+\frac{12}{18}\)

\(=\frac{1}{3}+\frac{2}{3}\)

\(=\frac{3}{3}\)

\(\Rightarrow=1\)

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

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

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

= \(\frac{4}{7}+2\)

= \(\frac{18}{7}\)

(7/15 + 8/15) + (9/16 + 7/16)

= 15/15 + 16/16

= 1 + 1

= 2

A = (2 + 2²) + (2³ + 2⁴ ) +…(2¹⁹⁹ + 2²⁰⁰)

A = 6 + 2² (2 + 2² ) +… + 2¹⁹⁸ (2 + 2²)

A = 6 + 2² (6 ) +… + 2¹⁹⁸ (6)

A = 6(1 + 2² +… + 2¹⁹⁸)

Vậy A chia hết cho 6

a) \(\left(\frac{2}{7}+\frac{3}{8}+\frac{12}{7}+\frac{5}{8}\right).\frac{19}{36}\)

\(=\left\{\left(\frac{2}{7}+\frac{12}{7}\right)+\left(\frac{3}{8}+\frac{5}{8}\right)\right\}.\frac{19}{36}\)

\(=\left(\frac{14}{7}+\frac{8}{8}\right).\frac{19}{36}\)

\(=\left(2+1\right).\frac{19}{36}\)

\(3.\frac{19}{36}=\frac{19}{12}\)