Question

tính bằng cách thuận tiện 

3 giờ 25 phút x 4 + 1 giờ 35 phút x 4

6,25 + 8,75 + 3,75 + 1,25 

0,215 x 74 ,24 + 25,76 x 0,215 + 18,5 

3/7:11/5+4/7:11/5

7,15 : 0,5 + 7,15 x 9 - 7,15

Answer 1

3 giờ 25 phút x 4 + 1 giờ 35 phút x 4

=(3h25' + 1h35') x 4

=5h x 4

=20 giờ

6,25 + 8,75 + 3,75 + 1,25 

\(=\left(6,25+3,75\right)+\left(8,75+1,25\right)=10+10=20\)

0,215 x 74 ,24 + 25,76 x 0,215 + 18,5 

\(=\left(74,24+25,76\right)x0,215+18,5\\ =100x0,215+18,5=21,5+18,5\\ =40\)

3/7:11/5+4/7:11/5

\(=\dfrac{3}{7}x\dfrac{5}{11}+\dfrac{4}{7}x\dfrac{5}{11}=\left(\dfrac{3}{7}+\dfrac{4}{7}\right)x\dfrac{5}{11}=\dfrac{7}{7}x\dfrac{5}{11}=1x\dfrac{5}{11}=\dfrac{5}{11}\)

7,15 : 0,5 + 7,15 x 9 - 7,15

\(=7,15x2+7,15x9-7,15x1\\ =7,15x\left(2+9-1\right)-7,15x10=71,5\)