Advertisements (Quảng cáo)
Bài 11 Tính
a) \({{ – 2} \over 7}.{{21} \over 8}\)
b) \(0,24.{{ – 15} \over 4}\)
c) \(\left( { – 2} \right).\left( { – {7 \over {12}}} \right)\)
d) \(\left( { – {3 \over {25}}} \right):6\)
Advertisements (Quảng cáo)
a) \({{ – 2} \over 7}.{{21} \over 8} = {{\left( { – 2} \right).21} \over {7.8}} = {{ – 42} \over {56}} = {{ – 3} \over 4}\)
b) \(0,24.{{ – 15} \over 4} = {{24} \over {100}}.{{ – 15} \over 4} = {6 \over {25}}.{{ – 15} \over 4} = {{6.\left( { – 15} \right)} \over {25.4}} = {{ – 90} \over {100}} = {{ – 9} \over {10}}\)
c) \(\left( { – 2} \right).\left( { – {7 \over {12}}} \right) = {{\left( { – 2} \right)\left( { – 7} \right)} \over {12}} = {{14} \over {12}} = {7 \over 6} = 1{1 \over 6}\)
d) \(\left( { – {3 \over {25}}} \right):6 = {{ – 3} \over {25}}:{6 \over 1} = {{ – 3} \over {25}}.{1 \over 6} = {{\left( { – 3} \right).1} \over {25.6}} = {{ – 3} \over {150}} = {{ – 1} \over {50}}\)