Chiều dài trồng được số khóm hoa là:
5,5:\(\dfrac{1}{4}\)=22(khóm hoa)
Chiều rộng trồng được số khóm hoa là:
3,75:\(\dfrac{1}{4}\)=15(khóm hoa)
Ta phải trừ đi 4 khóm hoa vì 4 khóm hoa ở 4 góc hình chữ nhật được đếm 2 lần nên ta có:
Số khóm hoa cần trồng là:
[(22+15).2]-4=70(khóm hoa)
Vậy: cần trồng 70 khóm hoa

 

a)\(\dfrac{1}{5}\)+\(\dfrac{4}{5}\):x=0,75
\(\dfrac{1}{5}\)+\(\dfrac{4}{5}\):x=\(\dfrac{3}{4}\)
\(\dfrac{4}{5}\):x=\(\dfrac{3}{4}\)-\(\dfrac{1}{5}\)
\(\dfrac{4}{5}\):x=\(\dfrac{15}{20}\)-\(\dfrac{4}{20}\)
\(\dfrac{4}{5}\):x=\(\dfrac{11}{20}\)
x=\(\dfrac{4}{5}\):\(\dfrac{11}{20}\)
x=\(\dfrac{4}{5}\).\(\dfrac{20}{11}\)
x=\(\dfrac{80}{55}\)=\(\dfrac{16}{11}\)
Vậy: x=\(\dfrac{16}{11}\)
b)x+\(\dfrac{1}{2}\)=1-x
2x=1-\(\dfrac{1}{2}\)
2x=\(\dfrac{2}{2}\)-\(\dfrac{1}{2}\)
2x=\(\dfrac{1}{2}\)
x=\(\dfrac{1}{2}\):2
x=\(\dfrac{1}{2}\).\(\dfrac{1}{2}\)
x=\(\dfrac{1}{4}\)
Vậy: x=\(\dfrac{1}{4}\)
 

\(\dfrac{2}{3}\).\(\dfrac{5}{4}\)-\(\dfrac{3}{4}\).\(\dfrac{2}{3}\)=\(\dfrac{2}{3}\).(\(\dfrac{5}{4}\)-\(\dfrac{3}{4}\))=\(\dfrac{2}{3}\).\(\dfrac{2}{4}\)=\(\dfrac{2}{3}\).\(\dfrac{1}{2}\)=\(\dfrac{1}{3}\)
b)2.(\(\dfrac{-3}{2}\))\(^2\)-\(\dfrac{7}{2}\)=2.\(\dfrac{9}{4}\)-\(\dfrac{7}{2}\)=\(\dfrac{18}{4}\)-\(\dfrac{7}{2}\)=\(\dfrac{9}{2}\)-\(\dfrac{7}{2}\)=\(\dfrac{2}{2}\)=1
c)-\(\dfrac{3}{4}\).\(5\dfrac{3}{13}\)-0,75.\(\dfrac{36}{13}\)=-\(\dfrac{3}{4}\).\(\dfrac{68}{13}\)-\(\dfrac{3}{4}\).\(\dfrac{36}{13}\)=-\(\dfrac{3}{4}\).(\(\dfrac{68}{13}\)+\(\dfrac{36}{13}\))=-\(\dfrac{3}{4}\).\(\dfrac{104}{13}\)=-\(\dfrac{3}{4}\).8=-\(\dfrac{24}{4}\)=-6