How long is a rectangular field with a width of 3/5 mile and an area of 21/50 square mile?
\(w=\frac{3}{5}mi\\\\l=?\\\\A_{\fbox{ }}=w\times l;\ A_{\fbox{ }}=\frac{21}{50}mi^2\\\\\frac{3}{5}l=\frac{21}{50}\ \ \ \ \ |multiply\ both\ sides\ by\ \frac{5}{3}\\\\l=\frac{21}{50}\times\frac{5}{3}\\\\l=\frac{7}{10}\\\\Answer:\boxed{\frac{7}{10}mi=0.7mi}\)
A = BL
A = 21/50 sq miles
B = 3/5 mile
L = ? mile
L = A/B
L = (21/50)/(3/5)
dividing by fraction is same as multiplying by it's reciprocal
L = (21/50)(5/3)
L = (215)/(503)
L = 105/150
divide both numerator & denominator by 5
L = 21/30
*divide both numerator & denominator by 3
L = 7/10 miles