bai bac ho
goi so hs cua lop la x (x≥5 )
so hs trong cay bang laf 5x
so hs trong cay phuong la $\frac{1}{3}$ .1phan2
vi con lai 5 hs trong cay tung nen ta cos pt
$\frac{1}{3}$ .1phan2=5
=30 EM HS
BAI 1
X=9cm
ta co $\frac{AB}{CD}$= $\frac{MN}{PQ}$
=$\frac{8}{6}$ =$\frac{12}{PQ}$
+=>PQ=9CM
BAI 2
Ap dung dinh ly ta-let co
$\frac{DQ}{QE}$= $\frac{DH}{DF}$
= $\frac{3}{4}$ =$\frac{4,5}{DF}$
<=>DF=6CM
<=> X= 6+4,5=10,5 cm
vay DF = 10,5 cm