Tính:
a) \(\displaystyle {5 \over 2} \times {1 \over 4} - {1 \over 8}\) b) \(\displaystyle {5 \over 2} + {1 \over 4} \times {1 \over 8}\)
c) \(\displaystyle {5 \over 2}:{1 \over 4} - {1 \over 8}\) d) \(\displaystyle {5 \over 2} + {1 \over 4}:{1 \over 8}\)
a) \(\displaystyle {5 \over 2} \times {1 \over 4} - {1 \over 8} = {5 \over 8} - {1 \over 8} = {4 \over 8} = {1 \over 2}\)
b) \(\displaystyle {5 \over 2} + {1 \over 4} \times {1 \over 8} = {5 \over 2} + {1 \over {32}} \displaystyle= {{80 } \over {32}} +\dfrac{1}{32}= {{81} \over {32}}\)
c) \(\displaystyle {5 \over 2}:{1 \over 4} - {1 \over 8} = {5 \over 2} \times {4 \over 1} - {1 \over 8} = {{20} \over 2} - {1 \over 8} \)
\(\displaystyle = 10 -\dfrac{1}{8} = {{80} \over 8} - \dfrac{1}{8}= {{79} \over 8}\)
d) \(\displaystyle {5 \over 2} + {1 \over 4}:{1 \over 8} = {5 \over 2} + {1 \over 4} \times {8 \over 1} = {5 \over 2} + {8 \over 4} \)
\(\displaystyle = {{5} \over 2}+2 = \dfrac{5}{2}+ \dfrac{4}{2} = {9 \over 2}\)
-- Mod Toán lớp 4