Question

tính bằng cách thuận tiện 

a)25x66+33x25+25

b)2/3x9/7+4/6x5/7-2/3

 

Answer 1

a, 25 \(\times\)66 + 33 \(\times\) 25 + 25

 = 25 \(\times\) 66 + 33 \(\times\) 25 + 25 \(\times\)1

= 25 \(\times\) ( 66 + 33 + 1)

= 25 \(\times\) ( 66 + 34)

= 25\(\times\) 100

2500

 

Answer 2

\(\dfrac{2}{3}\) \(\times\) \(\dfrac{9}{7}\) + \(\dfrac{4}{6}\) \(\times\) \(\dfrac{5}{7}\) - \(\dfrac{2}{3}\)

= \(\dfrac{2}{3}\) \(\times\) \(\dfrac{9}{7}\) + \(\dfrac{2}{3}\) \(\times\) \(\dfrac{5}{7}\) - \(\dfrac{2}{3}\) \(\times\) 1

= \(\dfrac{2}{3}\) \(\times\) ( \(\dfrac{9}{7}\) + \(\dfrac{5}{7}\) - 1)

= \(\dfrac{2}{3}\) \(\times\) ( 2 - 1)

= \(\dfrac{2}{3}\) \(\times\) 1

= \(\dfrac{2}{3}\)

Answer 3

25x66+33x25+25

=25x66+33x25+25x1

=25x(66+33+1)

=25x(66+340)

=25x10

=2500