tính bằng cách thuận tiện nhất: a) 1/10+2/20+3/30+4/40+5/50+6/60+7/70+8/80+9/90 b) 3,72+2,05+6,28+7,95 04/09/2021 Bởi Kinsley tính bằng cách thuận tiện nhất: a) 1/10+2/20+3/30+4/40+5/50+6/60+7/70+8/80+9/90 b) 3,72+2,05+6,28+7,95
a)1/10+2/20+3/30+4/40+5/50+6/60+7/70+8/80+9/90 =1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10 =9/10 b) 3,72+2,05+6,28+7,95 =(3,72+6,28)+(2,05+7,95) =10+10=20 Bình luận
Đáp án: a) $ \frac{9}{10}$ b) $20$ Giải thích các bước giải: a) $\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+ \frac{9}{90}$ $= \frac{1}{10}+\frac{1}{10}+ \frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}$ (rút gọn) $= \frac{1}{10}×9$ $= \frac{9}{10}$ b) $3,72+2,05+6,28+7,95$ $= (3,72 + 6,28) + (2,05+7,95)$ $= 10 + 10$ $= 20$ Bình luận
a)1/10+2/20+3/30+4/40+5/50+6/60+7/70+8/80+9/90
=1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10+1/10
=9/10
b) 3,72+2,05+6,28+7,95
=(3,72+6,28)+(2,05+7,95)
=10+10=20
Đáp án:
a) $ \frac{9}{10}$
b) $20$
Giải thích các bước giải:
a) $\frac{1}{10}+\frac{2}{20}+\frac{3}{30}+\frac{4}{40}+\frac{5}{50}+\frac{6}{60}+\frac{7}{70}+\frac{8}{80}+ \frac{9}{90}$
$= \frac{1}{10}+\frac{1}{10}+ \frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}+\frac{1}{10}$ (rút gọn)
$= \frac{1}{10}×9$
$= \frac{9}{10}$
b) $3,72+2,05+6,28+7,95$
$= (3,72 + 6,28) + (2,05+7,95)$
$= 10 + 10$
$= 20$