1.
\(3\dfrac{2}{5}=\dfrac{3
.
5+2}{5}=\dfrac{17}{5}\)
\(2\dfrac{4}{9}=\dfrac{2
.
9+4}{9}=\dfrac{22}{9}\)
\(7\dfrac{3}{8}=\dfrac{7
.
8+3}{8}=\dfrac{59}{8}\)
\(15\dfrac{1}{10}=\dfrac{15
.
10+1}{10}=\dfrac{151}{10}\)
2.
a. \(3\dfrac{5}{9}>2\dfrac{7}{9}\) b. \(5\dfrac{4}{10}=5\dfrac{2}{5}\) c. \(1\dfrac{2}{3}>1\dfrac{3}{5}\) d. \(4\dfrac{1}{8}>3\dfrac{3}{4}\)
3.
a. \(1\dfrac{1}{3}+2\dfrac{1}{2}=\dfrac{4}{3}+\dfrac{5}{2}=\dfrac{8}{6}+\dfrac{15}{6}=\dfrac{23}{6}\)
b. \(4\dfrac{2}{5}-1\dfrac{1}{10}=\dfrac{22}{5}-\dfrac{11}{10}=\dfrac{44}{10}-\dfrac{11}{10}=\dfrac{33}{10}\)
c. \(3\dfrac{1}{2}
.
1\dfrac{1}{7}=\dfrac{7}{2}
.
\dfrac{8}{7}=\dfrac{56}{14}=4\)
d. \(4\dfrac{1}{6}
:
2\dfrac{1}{3}=\dfrac{25}{6}
:
\dfrac{7}{3}=\dfrac{25}{6}
.
\dfrac{3}{7}=\dfrac{25}{14}\)
4.
3 giờ đầu Bắc chạy được số km là:
\(62
.
3=186\) (km)
4 giờ sau Bắc chạy được số km là:
\(55
.
4=220\) (km)
Tổng số giờ Bắc chạy xe là:
\(3+4=7\) (giờ)
Trung bình mỗi giờ Bắc chạy được số km là:
\(\left(186+220\right)
:
7=58\) (km)
ĐS:...............
3)
a)
=\(\dfrac{4}{3}\)+\(\dfrac{5}{2}\)
=\(\dfrac{8}{6}\)+\(\dfrac{15}{6}\)
=\(\dfrac{23}{6}\)
b)
=\(\dfrac{22}{5}\)-\(\dfrac{11}{10}\)
=\(\dfrac{44}{10}\)-\(\dfrac{11}{10}\)
=\(\dfrac{33}{10}\)
c)
=\(\dfrac{7}{2}\)x\(\dfrac{8}{7}\)
=4
d)
=\(\dfrac{25}{6}\):\(\dfrac{7}{3}\)
=\(\dfrac{25}{6}\)x\(\dfrac{3}{7}\)
=\(\dfrac{25}{14}\)
4 và 5